U.S. patent application number 11/402101 was filed with the patent office on 2006-10-12 for hydraulically driven working vehicle and hydraulic transaxle.
Invention is credited to Shinichi Hirose, Norihiro Ishii, Fumitoshi Ishino, Koji Iwaki, Hideaki Okada, Hiroshi Sugimoto, Hironori Sumomozawa, Shiro Ueno.
Application Number | 20060225927 11/402101 |
Document ID | / |
Family ID | 36648637 |
Filed Date | 2006-10-12 |
United States Patent
Application |
20060225927 |
Kind Code |
A1 |
Iwaki; Koji ; et
al. |
October 12, 2006 |
Hydraulically driven working vehicle and hydraulic transaxle
Abstract
In a hydraulic four-wheel drive vehicle, a rear transaxle
incorporates a hydraulic motor for driving rear wheels, a front
transaxle incorporates a hydraulic motor for driving front wheels,
and hydraulic pressure fluid pipes interposed between the front and
rear transaxles are extended along at least one of left and right
side plates of a frame of the vehicle.
Inventors: |
Iwaki; Koji; (Hyogo, JP)
; Ueno; Shiro; (Hyogo, JP) ; Ishii; Norihiro;
(Hyogo, JP) ; Okada; Hideaki; (Hyogo, JP) ;
Sugimoto; Hiroshi; (Hyogo, JP) ; Hirose;
Shinichi; (Hyogo, JP) ; Sumomozawa; Hironori;
(Hyogo, JP) ; Ishino; Fumitoshi; (Hyogo,
JP) |
Correspondence
Address: |
STERNE, KESSLER, GOLDSTEIN & FOX PLLC
1100 NEW YORK AVENUE, N.W.
WASHINGTON
DC
20005
US
|
Family ID: |
36648637 |
Appl. No.: |
11/402101 |
Filed: |
April 12, 2006 |
Current U.S.
Class: |
180/6.3 |
Current CPC
Class: |
B60K 17/105 20130101;
B60K 17/356 20130101; B60Y 2200/223 20130101 |
Class at
Publication: |
180/006.3 |
International
Class: |
B60K 17/10 20060101
B60K017/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2005 |
JP |
2005-114412 |
Jun 29, 2005 |
JP |
2005-190788 |
Claims
1. A hydraulically driven working vehicle comprising: a frame
including a pair of left and right side plates extended in the
fore-and-aft direction of the vehicle; a first transaxle supported
by one of front and rear portions of the frame, the first transaxle
including a hydraulic pump, a first hydraulic motor fluidly
connected to the hydraulic pump, a first axle driven by the first
hydraulic motor, and a first transaxle housing incorporating the
hydraulic pump, the first hydraulic motor and the first axle,
wherein the first transaxle housing is provided with a pair of
outwardly opened first ports fluidly connected to the hydraulic
pump and the first hydraulic motor, respectively; a second
transaxle supported by the other rear or front portion of the
frame, the second transaxle including a second hydraulic motor
fluidly connected to the hydraulic pump, a second axle driven by
the second hydraulic motor, and a second transaxle housing
swingably supported on the rear or front portion of the frame
through a center pivot, and incorporating the second hydraulic
motor and the second axle, wherein the second transaxle housing is
provided with a pair of second ports fluidly connected to the
second hydraulic motor; a prime mover supported by the frame
between the fist and second transaxles; a traveling power
transmission system supported by the frame between the prime mover
and the first transaxle so as to drivingly connect the hydraulic
pump to the prime mover; a working device disposed under the frame
between the first and second transaxles; a working power
transmission system supported by the frame between the prime mover
and the working device so as to drivingly connect the working
device to the prime mover; and a pair of axle-driving hydraulic
pressure fluid pipes interposed between the pair of first ports and
the pair of second ports so as to fluidly connect the second
hydraulic motor to the hydraulic pump, wherein the pipes include
respective fore-and-aft extended portions which are extended in the
fore-and-aft direction of the vehicle between an inside surface of
at least one of the left and right side plates of the frame and the
traveling and working power transmission systems.
2. The hydraulically driven working vehicle according to claim 1,
wherein the fore-and-aft extended portions of both of the pipes are
extended along the inside surface of one of the left and right side
plate.
3. The hydraulically driven working vehicle according to claim 1,
wherein the fore-and-aft extended portion of one of the pipes is
extended along the inside surface of one of the left and right side
plates, and the fore-and-aft extended portion of the other pipe is
extended along the inside surface of the other right or left side
plate.
4. The hydraulically driven working vehicle according to claim 3,
at least one of the pipes including: a first rigid pipe portion
connected to one of the first ports; a second rigid pipe portion
connected to one of the second ports; and a flexible pipe portion
interposed between the first and second rigid pipe portions,
wherein the flexible hose is extended along one of the left and
right side plates of the frame.
5. The hydraulically driven working vehicle according to claim 4,
further comprising: a stay supported on either the first transaxle
housing or one of the left and right side plates of the frame so as
to support the rigid pipe portion connected to the first port.
6. The hydraulically driven working vehicle according to claim 5,
wherein the first transaxle housing includes a boss connected to
the frame, and wherein the stay is mounted onto the boss.
7. The hydraulically driven working vehicle according to claim 4,
the at least one of the pipes further including: a swivel joint
disposed between the flexible pipe portion and at least one of the
first and second rigid pipe portions.
8. The hydraulically driven working vehicle according to claim 1,
at least one of the pipes including: a rigid pipe portion connected
to one of the first ports and extended along one of the left and
right side plates of the frame; and a flexible pipe portion
interposed between the rigid pipe portion and one of the second
ports.
9. The hydraulically driven working vehicle according to claim 8,
further comprising: a stay supported on either the first transaxle
housing or one of the left and right side plates of the frame so as
to support the rigid pipe portion.
10. The hydraulically driven working vehicle according to claim 9,
wherein the first transaxle housing includes a boss connected to
the frame, and wherein the stay is mounted onto the boss.
11. The hydraulically driven working vehicle according to claim 8,
the at least one of the pipes further including: a swivel joint
disposed between the flexible pipe portion and the rigid pipe
portion.
12. The hydraulically driven working vehicle according to claim 8,
wherein the pair of first ports are disposed at one of left and
right sides of the vehicle, wherein the pair of second ports are
disposed at the other right or left side of the vehicle, wherein
the fore-and-aft extended portion of at least one of the pipes is
extended along one of the left and right side plates of the frame
and connected to the second port, and wherein the at least one of
the pipes further includes a laterally extended portion which is
extended in the lateral direction of the vehicle between the first
port and the fore-and-aft extended portion of the at least one of
the pipe, further comprising: a stay fixed on the first transaxle
housing so as to support the laterally extended portion of the at
least one of the pipes.
13. The hydraulically driven working vehicle according to claim 12,
wherein the first transaxle housing includes a boss connected to
the frame, and wherein the stay is mounted onto the boss.
14. The hydraulically driven working vehicle according to claim 12,
the at least one of the pipes including: a first rigid pipe portion
connected to one of the first ports and serving as the laterally
extended portion of the at least one of the pipes; a second rigid
pipe portion connected to one of the second ports; and a flexible
pipe portion interposed between the first and second rigid pipe
portions, wherein the flexible hose is extended along one of the
left and right side plates of the frame.
15. The hydraulically driven working vehicle according to claim 14,
the at least one of the pipes further including: a swivel joint
disposed between the flexible pipe portion and the first rigid pipe
portion.
16. The hydraulically driven working vehicle according to claim 12,
wherein the fore-and-aft extended portions of both of the pipes are
extended along one of the left and right side plates of the frame
and connected to the respective second ports, wherein both of the
pipes include the respective laterally extended portions interposed
between the respective first ports and the respective fore-and-aft
extended portions thereof, and wherein the stay supports the
laterally extended portions of both of the pipes.
17. The hydraulically driven working vehicle according to claim 12,
wherein a first pipe of the pipes is extended in the fore-and-aft
direction of the vehicle from the corresponding first port along
one of left and right side plates of the frame, and wherein a
second pipe of the pipes includes the fore-and-aft extended portion
extended along the other right or left side plate and connected to
the corresponding second port, and includes the laterally extended
portion connected to the corresponding first port and supported by
the stay.
18. The hydraulically driven working vehicle according to claim 17,
further comprising: a stay fixed onto the one of the left and right
side plates so as to support the first pipe.
19. The hydraulically driven working vehicle according to claim 12,
at least one of the pipes including: a rigid pipe portion connected
to one of the first ports and extended along one of the left and
right side plates of the frame so as to serve as the fore-and-aft
extended portion; and a flexible pipe portion interposed between
the rigid pipe portion and one of the second ports.
20. The hydraulically driven working vehicle according to claim 19,
the at least one of the pipes further including: a swivel joint
disposed between the flexible pipe portion and the rigid pipe
portion.
21. The hydraulically driven working vehicle according to claim 19,
wherein the fore-and-aft extended portions of both of the pipes are
extended along one of the left and right side plates of the frame
and connected to the respective second ports, wherein both of the
pipes include respective laterally extended portions interposed
between the respective first ports and the respective fore-and-aft
extended portions thereof, further comprising: a stay fixed onto
the first transaxle housing so as to support the laterally extended
portions of both of the pipes.
22. The hydraulically driven working vehicle according to claim 12,
wherein a first pipe of the pipes is extended in the fore-and-aft
direction of the vehicle from the corresponding first port along
one of the left and right side plates of the frame, and wherein a
second pipe of the pipes includes the fore-and-aft extended portion
extended along the other right or left side plate and connected to
the corresponding second port, and includes a laterally extended
portion interposed between the corresponding first port and the
fore-and-aft extended portion thereof, further comprising: a stay
fixed onto the first transaxle housing so as to support the
laterally extended portion of the second pipe.
23. The hydraulically driven working vehicle according to claim 22,
further-comprising: a stay fixed onto the one of the left and right
side plates so as to support the first pipe.
24. The hydraulically driven working vehicle according to claim 1,
the first transaxle housing being provided with a pair of outwardly
opened third ports, further comprising: a hydraulic power steering
valve disposed on the frame between the first and second
transaxles; and a pair of power steering hydraulic pressure fluid
pipes interposed between the hydraulic power steering valve and the
pair of third ports and extended along at least one of the
axle-driving hydraulic pressure fluid pipes.
25. The hydraulically driven working vehicle according to claim 24,
wherein the pair of first ports and the pair of third ports are
disposed on the same side surface of the first transaxle
housing.
26. The hydraulically driven working vehicle according to claim 1,
the first transaxle further including: a center section disposed in
the first transaxle housing and interposed between the hydraulic
pump and the first hydraulic motor, the center section being
provided with a pair of first and second pump ports fluidly
connected to the hydraulic pump, a pair of first and second motor
ports fluidly connected to the first hydraulic motor, and a passage
interposed between the first pump port and the first motor port,
wherein the pair of first ports are fluidly connected to the second
pump port and the second motor port, respectively.
27. The hydraulically driven working vehicle according to claim 24,
the first transaxle further including: a charge pump disposed in
the first transaxle housing so as to be driven together with the
hydraulic pump by the power from the prime mover through the
traveling power transmission system, wherein one of the third ports
is fluidly connected to the charge pump, and wherein the other
third port is fluidly connected to a fluid-suction side of the
hydraulic pump.
28. The hydraulically driven working vehicle according to claim 27,
the first transaxle further including a charge pump casing
incorporating the charge pump, the charge pump casing being
disposed in the first transaxle housing and connected to the center
section, wherein the charge pump casing is provided with a passage
directly connected to the pair of third ports.
29. The hydraulically driven working vehicle according to claim 28,
wherein the charge pump casing is provided with another passage
directly connected to the pair of first ports so as to fluidly
connect the passage in the center section to the pair of first
ports.
30. The hydraulically driven working vehicle according to claim 28,
further comprising: an adapter attached onto the center section and
provided therein with a passage through which the pair of first
ports are fluidly connected to the center section.
31. A hydraulically driven working vehicle comprising: a frame
extended in the fore-and-aft direction of the vehicle; a first
transaxle supported by one of front and rear portions of the frame,
the first transaxle including a hydraulic pump, a first hydraulic
motor fluidly connected to the hydraulic pump, a first axle driven
by the first hydraulic motor, and a first transaxle housing
incorporating the hydraulic pump, the first hydraulic motor and the
first axle, wherein the first transaxle is formed therein with a
first fluid sump, and wherein the first transaxle housing is
provided with a pair of outwardly opened first ports fluidly
connected to the hydraulic pump and the first hydraulic motor,
respectively; a second transaxle supported by the other rear or
front portion of the frame, the second transaxle including a second
hydraulic motor fluidly connected to the hydraulic pump, a second
axle driven by the second hydraulic motor, and a second transaxle
housing incorporating the second hydraulic motor and the second
axle, wherein the second transaxle is formed therein with a second
fluid sump, and wherein the second transaxle housing is provided
with a pair of second ports fluidly connected to the second
hydraulic motor; a pair of hydraulic pressure fluid pipes
interposed between the pair of first ports and the pair of second
ports; a prime mover supported by the frame between the fist and
second transaxles; a traveling power transmission system supported
by the frame between the prime mover and the first transaxle so as
to drivingly connect the hydraulic pump to the prime mover; a
working device disposed under the frame between the first and
second transaxles; a working power transmission system supported by
the frame between the prime mover and the working device so as to
drivingly connect the working device to the prime mover; and a
reservoir tank fluidly connected to the hydraulic pump and the
first and second hydraulic motors, wherein the reservoir tank is
disposed so that a fluid level in the reservoir tank is higher than
levels of the first and second fluid sumps.
32. The hydraulically driven working vehicle according to claim 31,
wherein the reservoir tank is disposed just behind a rear end
surface of the frame.
33. The hydraulically driven working vehicle according to claim 32,
further comprising: a driver's seat; and a breather provided on a
top of the reservoir tank disposed behind the seat, wherein the
breather also serves as a fluid-supply opening of the reservoir
tank.
34. The hydraulically driven working vehicle according to claim 31,
further comprising: a fuel tank joined to the reservoir tank.
35. The hydraulically driven working vehicle according to claim 34,
further comprising: a driver's seat disposed above the first
transaxle, wherein the fuel tank and the reservoir tank are
disposed between the seat and the first transaxle.
36. The hydraulically driven working vehicle according to claim 35,
further comprising: a breather provided on a top of the reservoir
tank disposed behind the seat, wherein the breather also serves as
a fluid-supply opening of the reservoir tank.
37. The hydraulically driven working vehicle according to claim 31,
further comprising: a first wheel provided onto the first axle; and
a second wheel provided onto the second axle, wherein the reservoir
tank is disposed between the first and second wheels.
38. The hydraulically driven working vehicle according to claim 37,
further comprising: a bonnet incorporating the prime mover and the
reservoir tank.
39. The hydraulically driven working vehicle according to claim 38,
further comprising: a breather provided on a top of the reservoir
tank disposed behind the seat, wherein the breather also serves as
a fluid-supply opening of the reservoir tank; a dashboard provided
with an opening facing the top of the breather; and a removable lid
covering the opening of the dashboard.
40. A transaxle comprising: a transaxle housing supported by one of
front and rear portions of a vehicle body frame; a hydraulic pump
disposed in the transaxle housing so as to be driven by power from
a prime mover through a traveling power transmission system; a
charge pump disposed in the transaxle housing so as to be driven by
the power from the prime mover through the traveling power
transmission system; an axle disposed in the transaxle housing so
as to be driven by the hydraulic motor; a pair of first ports
provided on a side surface of the transaxle housing so as to be
fluidly connected to the hydraulic pump and the hydraulic motor
respectively; and a pair of second ports provided on the same side
surface of the transaxle housing with the first ports, wherein one
of the second ports is fluidly connected to the charge pump, and
the other second port is fluidly connected to a fluid-suction side
of the hydraulic pump.
41. The transaxle according to claim 40, further comprising: a
center section disposed in the transaxle housing and interposed
between the hydraulic pump and the hydraulic motor, the center
section being provided with a pair of first and second pump ports
fluidly connected to the hydraulic pump, a pair of first and second
motor ports fluidly connected to the hydraulic motor, and a passage
interposed between the first pump port and the first motor port,
wherein the pair of first ports are fluidly connected to the second
pump port and the second motor port, respectively.
42. The transaxle according to claim 40, further comprising: a
charge pump casing incorporating the charge pump, the charge pump
casing being disposed in the transaxle housing and connected to the
center section, wherein the charge pump casing is provided with a
passage directly connected to the pair of second ports.
43. The transaxle according to claim 42, wherein the charge pump
casing is provided with another passage directly connected to the
pair of first ports so as to fluidly connect the passage in the
center section to the pair of first ports.
44. The transaxle according to claim 42, further comprising: an
adapter attached onto the center section and provided therein with
a passage through which the pair of first ports are fluidly
connected to the center section.
45. The transaxle according to claim 40, further comprising: a pair
of third ports for fluidly connecting the pair of first ports to a
second hydraulic motor for driving another axle.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a hydraulically driven working
vehicle, especially, a four-wheel drive working vehicle, equipped
with front wheels and rear wheels driven by respective hydraulic
motors, and relates to a hydraulic transaxle including the
hydraulic motor applicable to the vehicle. An example of the
hydraulically driven working vehicle according to the invention is
a lawn tractor equipped at the middle body portion thereof with a
mower unit. The transaxle according to the invention can supply
fluid to hydraulic equipments equipped on the hydraulically driven
vehicle, e.g., a hydraulic power steering system, in addition to
the hydraulic motor for driving an axle.
[0003] 2. Related Art
[0004] Conventionally, there are well-known hydraulic four-wheel
drive working vehicles, each of which is equipped with front and
rear hydraulic motors for driving front wheels and rear wheels. A
hydraulic four-wheel drive working vehicle, as disclosed in
International Publication No. 2004/062956, is provided with a rear
transaxle including a hydraulic motor for driving left and right
rear wheels, and with a front transaxle including a pair of left
and right hydraulic motors for driving respective left and right
front steerable wheels. This type hydraulic four-wheel drive
working vehicle is equipped at a middle portion thereof between the
front and rear transaxles with a traveling power transmission
system for transmitting power from a prime mover to the rear
transaxle, and with a working power transmission system for
transmitting power from the prime mover to a working device. In
this situation, the front and rear transaxles are fluidly connected
to each other via pipes for driving the front and rear wheels
(axles), and the axle-driving pipes have to be disposed at the
middle portion without interfering with the traveling power
transmission system and the working power transmission system.
[0005] To miniaturizing the hydraulic four-wheel drive working
vehicle, the pipes are requested to be disposed within a space
inside a vehicle body frame. However, the space is mainly occupied
by the traveling power transmission system and the working power
transmission system. Further, the vehicle may be equipped under the
fore-and-aft middle portion of the vehicle body frame with a
working device, such as a mower unit.
[0006] The axle-driving pipes have to be disposed in the space
between the front and rear transaxles without interfering with the
traveling power transmission system and the working power
transmission system, and the working device at need. Further, to
facilitate assembly works, the pipes are desirably disposed so as
to require no device to be detached during the piping work of the
pipes, and to require no pipe to be detached during attachment of
other devices. On the other hand, in order to reduce internal
pressure resistance in the pipes, the pipes are requested to have
reduction of bent portions therein and to have rigid pipe portions
as long as possible. Especially, the pipes have to be prevented at
portions thereof adjacent to a center pivot of the front transaxle
with being excessively twisted or bent, and prevented at portions
thereof connected to ports from having oil leak or being
damaged.
[0007] If the hydraulic four-wheel drive vehicle includes a
hydraulic power steering system, hydraulic fluid pipes for the
power steering system must be disposed so as to solve the same
problems as the axle-driving pipes.
[0008] Further, if the vehicle is provided with a reservoir tank
for supplying fluid to the hydraulic motors in the front and rear
transaxles, it is requested that the reservoir tank is disposed so
as to be prevented from interfering with the traveling power
transmission system and the working power transmission system, to
have easy oiling and maintenance, and to effectively supply fluid
into the housings of the front and rear transaxles. Especially,
when the front transaxle housing is swingably supported onto the
vehicle body frame via a center pivot, the reservoir tank is
requested to prevent fluid therein from being contaminated with air
by tilt of the fluid level surface according to the swing of the
front transaxle housing, and to prevent hydraulic pressure fluid
pipes between the reservoir tank and the transaxles from being
twisted by the swing of the front transaxle housing.
SUMMARY OF THE INVENTION
[0009] A first object of the invention is to provide a hydraulic
four-wheel drive working vehicle with a simple hydraulic pressure
piping structure solving the above problems.
[0010] To achieve the first object, in a first aspect of the
invention, a hydraulically driven working vehicle comprises: a
frame including a pair of left and right side plates extended in
the fore-and-aft direction of the vehicle; a first transaxle
supported by one of front and rear portions of the frame, the first
transaxle including a hydraulic pump, a first hydraulic motor
fluidly connected to the hydraulic pump, a first axle driven by the
first hydraulic motor, and a first transaxle housing incorporating
the hydraulic pump, the first hydraulic motor and the first axle,
wherein the first transaxle housing is provided with a pair of
outwardly opened first ports fluidly connected to the hydraulic
pump and the first hydraulic motor, respectively; a second
transaxle supported by the other rear or front portion of the
frame, the second transaxle including a second hydraulic motor
fluidly connected to the hydraulic pump, a second axle driven by
the second hydraulic motor, and a second transaxle housing
swingably supported on the rear or front portion of the frame
through a center pivot, and incorporating the second hydraulic
motor and the second axle, wherein the second transaxle housing is
provided with a pair of second ports fluidly connected to the
second hydraulic motor; a prime mover supported by the frame
between the fist and second transaxles; a traveling power
transmission system supported by the frame between the prime mover
and the first transaxle so as to drivingly connect the hydraulic
pump to the prime mover; a working device disposed under the frame
between the first and second transaxles; a working power
transmission system supported by the frame between the prime mover
and the working device so as to drivingly connect the working
device to the prime mover; and a pair of axle-driving hydraulic
pressure fluid pipes interposed between the pair of first ports and
the pair of second ports so as to fluidly connect the second
hydraulic motor to the hydraulic pump. The pipes include respective
fore-and-aft extended portions which are extended in the
fore-and-aft direction of the vehicle between an inside surface of
at least one of the left and right side plates of the frame and the
traveling and working power transmission systems.
[0011] In the vehicle according to the first aspect, the
axle-driving hydraulic pressure fluid pipes disposed so as not to
be exposed sideward from the frame vehicle, thereby being portected
from external obstacles. Consequently, the traveling performance of
the vehicle can be safely maintained. Further, the vehicle has good
appearance because of the hidden pipes.
[0012] In the vehicle according to the first aspect, preferably,
the fore-and-aft extended portions of both of the pipes are
extended along the inside surface of one of the left and right side
plate. Due to the simple arrangement of the pipes in the narrow
space along the inside surface of the side plate, the vehicle can
be minimized while ensuring prevention of the pipes from
interfering with the traveling and working power transmission
systems and the working device. Further, the piping work for this
arrangement of the pipes can be easy.
[0013] Alternatively, in the vehicle according to the first aspect,
preferably, the fore-and-aft extended portion of one of the pipes
is extended along the inside surface of one of the left and right
side plates, and the fore-and-aft extended portion of the other
pipe is extended along the inside surface of the other right or
left side plate. Due to the simple arrangement of the pipes in the
narrow spaces along the inside surfaces of the side plates, the
vehicle can be minimized while ensuring prevention of the pipes
from interfering with the traveling and working power transmission
systems and the working device. Further, the piping work for this
arrangement of the pipes can be easy.
[0014] Further preferably, at least one of the pipes includes: a
first rigid pipe portion connected to one of the first ports; a
second rigid pipe portion connected to one of the second ports; and
a flexible pipe portion interposed between the first and second
rigid pipe portions. The flexible hose is extended along one of the
left and right side plates of the frame. Therefore, the flexible
hose can be bent or curved so as to absorb stress on the pipe
according to the swing of the second transaxle around the center
pivot. Consequently, the at least one pipe can be durable against
the frequent swing of the second transaxle.
[0015] Alternatively, preferably, at least one of the pipes
includes: a rigid pipe portion connected to one of the first ports
and extended along one of the left and right side plates of the
frame; and a flexible pipe portion interposed between the rigid
pipe portion and one of the second ports. Consequently, the main
portion of the at least one pipe is the rigid pipe portion whose
internal pressure resistance is small so as to ensure good fuel
efficiency.
[0016] In either of the above two cases where the at least one pipe
uses the rigid pipe portion, preferably, a stay is supported on
either the first transaxle housing or one of the left and right
side plates of the frame so as to support the rigid pipe portion
connected to the first port. Therefore, the stay prevents warp of
the pipe caused by the swing of the second transaxle around the
center pivot from being transmitted to the end of the pipe
connected to the corresponding first port, thereby preventing the
pipe end and the first port from having oil leak and from being
damaged.
[0017] Further preferably, the first transaxle housing includes a
boss connected to the frame, and the stay is mounted onto the boss.
Consequently, due to the support by the stay on the first transaxle
housing, the pipe end and the first port connected to each other
are further surely prevented from moving relative to each other
causing the oil leak and damage. The boss ordinarily formed on the
first transaxle housing serves as a fixture portion onto which the
stay is fixed, thereby requiring no additional fixture member and
saving costs.
[0018] Further preferably, the at least one of the pipes further
includes a swivel joint disposed between the flexible pipe portion
and at least one of the first and second rigid pipe portions. The
swivel joint absorbs twist of the pipe caused by the swing of the
second transaxle around the center pivot, thereby inexpensively
providing the pipe having high durability against the swing of the
second transaxle.
[0019] Alternatively, in the vehicle according to the first aspect,
preferably, the pair of first ports are disposed at one of left and
right sides of the vehicle, and the pair of second ports are
disposed at the other right or left side of the vehicle. The
fore-and-aft extended portion of at least one of the pipes is
extended along one of the left and right side plates of the frame
and connected to the second port. The at least one of the pipes
further includes a laterally extended portion which is extended in
the lateral direction of the vehicle between the first port and the
fore-and-aft extended portion of the at least one of the pipe. A
stay is fixed on the first transaxle housing so as to support the
laterally extended portion of the at least one of the pipes.
[0020] Therefore, in the case that the pair of first ports and the
pair of second ports are opened laterally opposite to each other,
the limited spaces along the left and right side plates are used
for piping of the axle-driving pipes without interfering with
another equipment, thereby miniaturizing the vehicle. Further, the
stay prevents warp of the corresponding pipe caused by the swing of
the second transaxle around the center pivot from being transmitted
to the end of the pipe connected to the corresponding first port,
thereby preventing the pipe end and the first port from having oil
leak and from being damaged.
[0021] Further preferably, the first transaxle housing includes a
boss connected to the frame, and wherein the stay is mounted onto
the boss. Consequently, due to the support by the stay on the first
transaxle housing, the pipe end and the first port connected to
each other are further surely prevented from moving relative to
each other causing the oil leak and damage. The boss ordinarily
formed on the first transaxle housing serves as a fixture portion
onto which the stay is fixed, thereby requiring no additional
fixture member and saving costs.
[0022] Further preferably, the at least one of the pipes includes:
a first rigid pipe portion connected to one of the first ports and
serving as the laterally extended portion of the at least one of
the pipes; a second rigid pipe portion connected to one of the
second ports; and a flexible pipe portion interposed between the
first and second rigid pipe portions, wherein the flexible hose is
extended along one of the left and right side plates of the frame.
Therefore, the flexible hose can be bent or curved so as to absorb
stress on the pipe according to the swing of the second transaxle
around the center pivot. Consequently, the at least one pipe can be
durable against the frequent swing of the second transaxle.
[0023] Alternatively, further preferably, the at least one of the
pipes includes: a rigid pipe portion connected to one of the first
ports and extended along one of the left and right side plates of
the frame so as to serve as the fore-and-aft extended portion; and
a flexible pipe portion interposed between the rigid pipe portion
and one of the second ports. Consequently, the main portion of the
at least one pipe is the rigid pipe portion whose internal pressure
resistance is small so as to ensure good fuel efficiency.
[0024] In either of the above two cases where the at least one pipe
includes the rigid pipe portion and the flexible pipe portion, the
at least one of the pipes further includes a swivel joint disposed
between the flexible pipe portion and the first rigid pipe portion.
The swivel joint absorbs twist of the pipe caused by the swing of
the second transaxle around the center pivot, thereby inexpensively
providing the pipe having high durability against the swing of the
second transaxle.
[0025] In the pipe arrangement when the pair of first ports and the
pair of second ports are laterally offset, preferably, the
fore-and-aft extended portions of both of the pipes are extended
along one of the left and right side plates of the frame and
connected to the respective second ports. Both of the pipes include
the respective laterally extended portions interposed between the
respective first ports and the respective fore-and-aft extended
portions thereof. The stay supports the laterally extended portions
of both of the pipes. Therefore, both of the fore-and-aft extended
portions of the pipes are juxtaposed in the limited space along the
side plate so as to minimize the vehicle. Further, the stay
prevents warp of both of the pipes caused by the swing of the
second transaxle around the center pivot from being transmitted to
the ends of the pipes connected to the respective first ports,
thereby preventing the pipe ends and the first ports from having
oil leak and from being damaged.
[0026] In the pipe arrangement when the pair of first ports and the
pair of second ports are laterally offset, alternatively,
preferably, a first pipe of the pipes is extended in the
fore-and-aft direction of the vehicle from the corresponding first
port along one of left and right side plates of the frame, and a
second pipe of the pipes includes the fore-and-aft extended portion
extended along the other right or left side plate and connected to
the corresponding second port, and includes the laterally extended
portion connected to the corresponding first port and supported by
the stay. Therefore, the fore-and-aft extended portions of the
pipes are disposed in the limited spaces along the respective left
and right side plates so as to minimize the vehicle. Further, the
stay prevents warp of the second pipe caused by the swing of the
second transaxle around the center pivot from being transmitted to
the end of the second pipe connected to the first port, thereby
preventing the end of the second pipe and the first port from
having oil leak and from being damaged.
[0027] Further preferably, a stay is fixed onto the one of the left
and right side plates so as to support the first pipe. The stay on
the side plate prevents warp of the first pipe, which is not
supported by the stay on the first transaxle housing, caused by the
swing of the second transaxle around the center pivot from being
transmitted to the end of the first pipe connected to the first
port, thereby preventing the end of the first pipe and the first
port from having oil leak and from being damaged.
[0028] In the vehicle according to the first aspect, preferably,
the first transaxle housing is provided with a pair of outwardly
opened third ports, a hydraulic power steering valve is disposed on
the frame between the first and second transaxles, and a pair of
power steering hydraulic pressure fluid pipes are interposed
between the hydraulic power steering valve and the pair of third
ports and extended along at least one of the axle-driving hydraulic
pressure fluid pipes. Therefore, the space required for piping the
pair of axle-driving hydraulic pressure fluid pipes and the pair of
power steering hydraulic pressure fluid pipes and the at least one
axle-driving hydraulic pressure pipe is saved.
[0029] In the vehicle according to the first aspect, preferably,
the pair of first ports and the pair of third ports are disposed on
the same side surface of the first transaxle housing. Consequently,
the pair of power steering hydraulic pressure fluid pipes and the
at least one axle-driving hydraulic pressure fluid pipe are
compactly collected in the vicinity of the first transaxle so as to
be connected to the respective third ports and the corresponding
first port.
[0030] In the vehicle according to the first aspect, the first
transaxle further includes a center section disposed in the first
transaxle housing and interposed between the hydraulic pump and the
first hydraulic motor. The center section is provided with a pair
of first and second pump ports fluidly connected to the hydraulic
pump, a pair of first and second motor ports fluidly connected to
the first hydraulic motor, and a passage interposed between the
first pump port and the first motor port. The pair of first ports
are fluidly connected to the second pump port and the second motor
port, respectively. Due to the center section, the component
devices such as the hydraulic pump and the first hydraulic motor
and the passage for connection of the hydraulic pump, the first
hydraulic motor and the first ports are compactly assembled
together so as to minimize the first transaxle housing and expand
the space for piping.
[0031] Further preferably, the first transaxle further includes a
charge pump disposed in the first transaxle housing so as to be
driven together with the hydraulic pump by the power from the prime
mover through the traveling power transmission system. One of the
third ports is fluidly connected to the charge pump, and the other
third port is fluidly connected to a fluid-suction side of the
hydraulic pump. Due to the charge pump, no additional device for
supplying fluid to a hydraulic power steering actuator is required
so as to expand an area in the limited space for piping the
axle-driving and power steering hydraulic pressure fluid pipes, and
save costs.
[0032] Further preferably, the first transaxle further includes a
charge pump casing incorporating the charge pump. The charge pump
casing is disposed in the first transaxle housing and connected to
the center section. The charge pump casing is provided with a
passage directly connected to the pair of third ports. Due to the
charge pump casing, the charge pump and associated equipments are
compactly collected so as to minimize the first transaxle housing,
thereby expanding the space for piping the axle-driving and power
steering hydraulic pressure fluid pipes.
[0033] Further preferably, the charge pump casing is provided with
another passage directly connected to the pair of first ports so as
to fluidly connect the passage in the center section to the pair of
first ports. Therefore, the inside portion of the charge pump
casing is used for forming the passage directly connected to the
first ports disposed on the same side surface of the first
transaxle housing with the third ports, so as to reduce a space in
the first transaxle housing for a passage interposed between the
third ports and the first ports, i.e., minimize the first transaxle
housing, thereby expanding the space for piping the axle-driving
and power steering hydraulic pressure fluid pipes.
[0034] Further preferably, an adapter is attached onto the center
section and provided therein with a passage through which the pair
of first ports are fluidly connected to the center section. Due to
the easily removable adapter, the passage directly connected to the
first ports disposed on the same side surface of the first
transaxle housing with the third ports can be easily formed, and a
space in the first transaxle housing for a passage interposed
between the third ports and the first ports is reduced, that is,
the first transaxle housing is minimized, thereby expanding the
space for piping the axle-driving and power steering hydraulic
pressure fluid pipes.
[0035] A second object of the invention is to provide a hydraulic
four-wheel drive working vehicle equipped with a reservoir tank
which prevents fuel therein from being contaminated with air so as
to solve the above problems.
[0036] To achieve the second object, in a second aspect of the
invention, a hydraulically driven working vehicle comprises: a
frame extended in the fore-and-aft direction of the vehicle; a
first transaxle supported by one of front and rear portions of the
frame, the first transaxle including a hydraulic pump, a first
hydraulic motor fluidly connected to the hydraulic pump, a first
axle driven by the first hydraulic motor, and a first transaxle
housing incorporating the hydraulic pump, the first hydraulic motor
and the first axle, wherein the first transaxle is formed therein
with a first fluid sump, and wherein the first transaxle housing is
provided with a pair of outwardly opened first ports fluidly
connected to the hydraulic pump and the first hydraulic motor,
respectively; a second transaxle supported by the other rear or
front portion of the frame, the second transaxle including a second
hydraulic motor fluidly connected to the hydraulic pump, a second
axle driven by the second hydraulic motor, and a second transaxle
housing incorporating the second hydraulic motor and the second
axle, wherein the second transaxle is formed therein with a second
fluid sump, and wherein the second transaxle housing is provided
with a pair of second ports fluidly connected to the second
hydraulic motor; a pair of hydraulic pressure fluid pipes
interposed between the pair of first ports and the pair of second
ports; a prime mover supported by the frame between the fist and
second transaxles; a traveling power transmission system supported
by the frame between the prime mover and the first transaxle so as
to drivingly connect the hydraulic pump to the prime mover; a
working device disposed under the frame between the first and
second transaxles; a working power transmission system supported by
the frame between the prime mover and the working device so as to
drivingly connect the working device to the prime mover; and a
reservoir tank fluidly connected to the hydraulic pump and the
first and second hydraulic motors. The reservoir tank is disposed
so that a fluid level in the reservoir tank is higher than levels
of the first and second fluid sumps. Therefore, fluid flowing from
the reservoir tank to the first or second transaxle housing is
prevented from being contaminated with air.
[0037] In the vehicle according to the second aspect, preferably,
the reservoir tank is disposed just behind a rear end surface of
the frame. Therefore, the reservoir tank exposed on the frame can
be easily attached or detached onto and from the frame, and easily
subjected to maintenance. Further, the reservoir tank can be
disposed behind rear wheel tires so that the rear wheel tires do
not hinder the attachment, detachment and maintenance of the
reservoir tank, and the damage of the reservoir tank by mud and
stones stuck on the tire is reduced.
[0038] Alternatively, in the vehicle according to the second
aspect, preferably, a breather provided on a top of the reservoir
tank, which also serves as a fluid-supply opening of the reservoir
tank, is disposed behind a driver's seat of the vehicle. Therefore,
the top of the breather disposed outward of the vehicle facilitate
fluid-supply to the reservoir tank.
[0039] In the vehicle according to the second aspect, preferably, a
fuel tank is joined to the reservoir tank. Therefore, the number of
required component parts is reduced so as to facilitate assembling
work of the vehicle.
[0040] Further preferably, a driver's seat is disposed above the
first transaxle, so that the fuel tank and the reservoir tank are
disposed between the seat and the first transaxle. Therefore, the
space between the first transaxle and the seat above the first
transaxle is effectively used for arranging the reservoir tank so
as to reduce a dead space, thereby minimizing the vehicle.
[0041] Further preferably, a breather provided on a top of the
reservoir tank, which also serves as a fuel-support opening of the
reservoir tank, is disposed behind the seat. Therefore, fuel can be
easily supplied to the reservoir tank.
[0042] Alternatively, in the vehicle according to the second
aspect, the reservoir tank is disposed between a first wheel
provided onto the first axle and a second wheel provided onto the
second axle. This arrangement of the heavy reservoir tank improves
the weight balance of the vehicle in the fore-and-aft
direction.
[0043] Further preferably, a bonnet incorporating the prime mover
also incorporates the reservoir tank. Therefore, the inner space of
the bonnet is effectively used for arranging the reservoir tank so
as to minimize the vehicle. Further, the cooling wind for the prime
mover in the bonnet can also cool the reservoir tank, thereby
requiring no additional device for cooling the reservoir tank.
[0044] Further preferably, a breather provided on a top of the
reservoir tank, which also serves as a fluid-supply opening of the
reservoir tank, is disposed behind the seat. A dashboard of the
vehicle is provided with an opening, which faces the top of the
breather and is covered with a removable lid. Due to such a simple
structure, fuel can be easily supplied through the dashboard into
the reservoir tank.
[0045] A third object is to provide a hydraulic transaxle, which
can serve as a main transaxle of a hydraulic four-wheel working
vehicle, adapted to prevent pipes therearound from being
complicated.
[0046] To achieve the third object, in a third aspect of the
invention, a transaxle comprises: a transaxle housing supported by
one of front and rear portions of a vehicle body frame; a hydraulic
pump disposed in the transaxle housing so as to be driven by power
from a prime mover through a traveling power transmission system; a
charge pump disposed in the transaxle housing so as to be driven by
the power from the prime mover through the traveling power
transmission system; an axle disposed in the transaxle housing so
as to be driven by the hydraulic motor; a pair of first ports
provided on a side surface of the transaxle housing so as to be
fluidly connected to the hydraulic pump and the hydraulic motor
respectively; and a pair of second ports provided on the same side
surface of the transaxle housing with the first ports. One of the
second ports is fluidly connected to the charge pump, and the other
second port is fluidly connected to a fluid-suction side of the
hydraulic pump.
[0047] Therefore, hydraulic pressure fluid pipes for driving an
auxiliary device (such as a power steering actuator) connected to
the second ports can be compactly collected together with hydraulic
pressure fluid pipes for driving the axle of the first transaxle
connected to the pair of first ports. Further, due to the charge
pump, the auxiliary device (such as the power steering actuator)
requires no additional fluid-supply device so as to save a space,
i.e., to expand the space for the pipes, and to save the number of
parts and costs.
[0048] In the transaxle according to the third aspect, preferably,
a center section is disposed in the transaxle housing and
interposed between the hydraulic pump and the hydraulic motor. The
center section is provided with a pair of first and second pump
ports fluidly connected to the hydraulic pump, a pair of first and
second motor ports fluidly connected to the hydraulic motor, and a
passage interposed between the first pump port and the first motor
port. The pair of first ports are fluidly connected to the second
pump port and the second motor port, respectively. Due to the
center section, the component devices such as the hydraulic pump
and the first hydraulic motor and the passage for connection of the
hydraulic pump, the first hydraulic motor and the first ports are
compactly assembled together so as to minimize the transaxle
housing and expand the space for pipes connected to the first ports
and the second ports.
[0049] In the transaxle according to the third aspect, preferably,
a charge pump casing incorporating the charge pump is disposed in
the transaxle housing and connected to the center section. The
charge pump casing is provided with a passage directly connected to
the pair of second ports. Due to the charge pump casing, the charge
pump and associated equipments are compactly collected so as to
minimize the transaxle housing, thereby expanding the space for
pipes connected to the first ports and the second ports.
[0050] Further preferably, the charge pump casing is provided with
another passage directly connected to the pair of first ports so as
to fluidly connect the passage in the center section to the pair of
first ports. Therefore, the inside portion of the charge pump
casing is used for forming the passage directly connected to the
first ports disposed on the same side surface of the transaxle
housing with the second ports, so as to reduce a space in the
transaxle housing for a passage interposed between the second ports
and the first ports, i.e., minimize the transaxle housing, thereby
expanding the space for pipes connected to the first ports and the
second ports.
[0051] Alternatively, further preferably, an adapter is attached
onto the center section and provided therein with a passage through
which the pair of first ports are fluidly connected to the center
section. Due to the easily removable adapter, the passage directly
connected to the first ports disposed on the same side surface of
the transaxle housing with the second ports can be easily formed,
and a space in the transaxle housing for a passage interposed
between the second ports and the first ports is reduced, that is,
the transaxle housing is minimized, thereby expanding the space for
pipes connected to the first ports and the second ports.
[0052] In the transaxle according to the third aspect, preferably,
a pair of third ports is provided for fluidly connecting the pair
of first ports to a second hydraulic motor for driving another
axle. Due to this arrangement, a vehicle equipped with the
transaxle can be provided with compactly collected hydraulic
pressure fluid pipes, thereby being minimized.
[0053] These, further and other objects, features and advantages
will appear more fully from the following description with
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] FIG. 1 is a sectional side view of a hydraulic four-wheel
drive working vehicle according to a first embodiment of the
invention.
[0055] FIG. 2 is a hydraulic circuit diagram of the hydraulic
four-wheel drive working vehicle according to the invention.
[0056] FIG. 3 is a sectional plan view of the hydraulic four-wheel
drive working vehicle according to the first embodiment, provided
with an arrangement of hydraulic pressure fluid pipes.
[0057] FIG. 4 is a sectional view of a pipe stay support
portion.
[0058] FIG. 5 is a sectional plan view of a rear transaxle provided
on a left side surface thereof with hydraulic fluid
supply-and-delivery ports.
[0059] FIG. 6 is a sectional plan view of a rear transaxle provided
on a right side surface thereof with hydraulic fluid
supply-and-delivery ports facing forward.
[0060] FIG. 7 is-a sectional plan view of a rear transaxle provided
on a left side surface thereof with hydraulic fluid
supply-and-delivery ports facing forward.
[0061] FIG. 8 is a rear view of a front transaxle.
[0062] FIG. 9 is a sectional plan view of the hydraulic four-wheel
drive working vehicle according to the first embodiment, provided
with another arrangement of hydraulic pressure fluid pipes.
[0063] FIG. 10 is a sectional plan view of a hydraulic four-wheel
drive working vehicle according to a second embodiment of the
invention, provided with an arrangement of hydraulic pressure fluid
pipes.
[0064] FIG. 11 is a sectional plan view of the hydraulic four-wheel
drive working vehicle according to the second embodiment, provided
with another arrangement of hydraulic pressure fluid pipes.
[0065] FIG. 12 is a sectional plan view of a hydraulic four-wheel
drive working vehicle according to a third embodiment of the
invention, provided with an arrangement of hydraulic pressure fluid
pipes.
[0066] FIG. 13 is a sectional plan view of the hydraulic four-wheel
drive working vehicle according to the third embodiment, provided
with another arrangement of hydraulic pressure fluid pipes.
[0067] FIG. 14 is a sectional side view of a hydraulic four-wheel
drive working vehicle according to a fourth embodiment of the
invention, provided with an arrangement of a reservoir tank.
[0068] FIG. 15 is a sectional side view of a hydraulic four-wheel
drive working vehicle according to a fifth embodiment, provided
with another arrangement of a reservoir tank.
[0069] FIG. 16 is a right side view of a rear transaxle for the
vehicle according to the first embodiment.
[0070] FIG. 17 is a left side view of the rear transaxle according
to the first embodiment.
[0071] FIG. 18 is a sectional right side view of the rear transaxle
according to the first embodiment, showing a center section and a
charge pump casing in a transaxle housing.
[0072] FIG. 19 is a cross sectional view of the rear transaxle
taken along an A-A line of FIG. 17.
[0073] FIG. 20 is a cross sectional view of the rear transaxle
taken along a B-B line of FIG. 17.
[0074] FIG. 21 is a cross sectional view of the rear transaxle
taken along a C-C line of FIG. 17.
[0075] FIG. 22 is a cross sectional view of the rear transaxle
taken along a D-D line of FIG. 17.
[0076] FIG. 23 is a cross sectional view of the rear transaxle
taken along an E-E line of FIG. 17.
[0077] FIG. 24(a) is a plan view of a bottom surface of the center
section joined to the charge pump casing, and FIG. 24(b) is a plan
view of a top surface of the charge pump casing joined to the
center section.
[0078] FIG. 25 is another hydraulic circuit diagram of a rear
transaxle separated from a pump housing.
[0079] FIG. 26 is a right side view of a rear transaxle according
to a sixth embodiment.
[0080] FIG. 27 is a sectional plan view of the rear transaxle
according to the sixth embodiment.
[0081] FIG. 28 is a sectional right side view of the rear transaxle
according to the sixth embodiment, showing a center section and a
charge pump casing in a transaxle housing.
[0082] FIG. 29 is a cross sectional view of the rear transaxle
taken along an A-A line of FIG. 27.
[0083] FIG. 30 is a cross sectional view of the rear transaxle
taken along a B-B line of FIG. 27.
[0084] FIG. 31(a) is a sectional plan view of the charge pump
casing in the rear transaxle according to the sixth embodiment, and
FIG. 31(b) is a sectional side view of the charge pump casing.
[0085] FIG. 32(a) is a plan view of a bottom surface of the center
section joined to the charge pump casing, and FIG. 32(b) is a plan
view of a top surface of the charge pump casing joined to the
center section, wherein the center section and the charge pump
casing are provided for the rear transaxle according to the sixth
embodiment.
[0086] FIG. 33(a) is a sectional side view of a pipe connecter
fitted in a transaxle housing, and FIG. 33(b) is a sectional side
view of another pipe connecter fitted in a transaxle housing.
DETAILED DESCRIPTION OF THE INVENTION
First Embodiment
[0087] Referring to FIGS. 1 to 3, a hydraulic four-wheel drive
working vehicle 100 according to a first embodiment of the
invention will be described. Vehicle 100 is an Ackerman type
steered lawn tractor, comprising: a frame 3; a rear transaxle 1; a
front transaxle 2; an engine 10; a traveling power transmission
system; a mower unit 20; and a mower driving power transmission
system. Frame 3 includes parallel left and right side plates 3L and
3R extended in the fore-and-aft direction of vehicle 100.
[0088] Rear transaxle 1 is supported by a rear portion of frame 3.
Rear transaxle 1 includes a rear transaxle housing 1H,
incorporating a hydraulic pump P, a hydraulic motor M1 (serving as
a first hydraulic motor) fluidly connected to hydraulic pump P,
left and right rear wheel axles 6 (serving as a first axle), and a
deceleration gear train 37 and a differential gear unit 38 (see
FIG. 2) interposed between hydraulic motor M1 and axles 6. Rear
transaxle housing 1H is outwardly opened by a pair of traveling
hydraulic fluid supply-and-delivery ports 1a and 1b, which are
connected to hydraulic pump P and hydraulic motor M1,
respectively.
[0089] Front transaxle 2 is supported by a front portion of frame
3. Front transaxle 2 includes a front transaxle housing 2H
swingably supported onto frame 3 through a center pivot 5. Front
transaxle housing 2H incorporates a pair of hydraulic motors M2 and
M3, and left and right front wheel axles 8 driven by respective
hydraulic motors M2 and M3. Front transaxle housing 2H is outwardly
opened by a pair of traveling hydraulic fluid supply-and-delivery
ports 2a and 2b, which are fluidly connected to respective
hydraulic motors M2 and M3, so as to fluidly connect hydraulic
motors M2 and M3 to hydraulic pump P in rear transaxle 1.
[0090] Engine 10 is supported by frame 3 between rear and front
transaxles 1 and 2. The traveling power transmission system for
drivingly connecting hydraulic pump P to engine 10 is supported by
frame 3 between engine 10 and rear transaxle 1.
[0091] Mower unit 20 is disposed under frame 3 between rear and
front transaxles 1 and 2. The mower driving power transmission
system for drivingly connecting mower unit 20 to engine 10 is
supported by frame 3 between engine 10 and mower unit 20.
[0092] Vehicle 100 is provided with a pair of axle-driving
hydraulic pressure fluid pipes 23 and 26 interposed between the
pair of ports 1a and 1b and the pair of ports 2a and 2b so as to
fluidly connect hydraulic motors M2 and M3 to hydraulic pump P. In
this embodiment, ports 1a and 1b of rear transaxle housing 1H are
disposed rightward of vehicle 100, and ports 2a and 2b of front
transaxle housing 2H are disposed leftward of vehicle 100. Pipes 23
and 26 are extended laterally (in the left-and-right direction)
from respective ports 1a and 1b, and extended in the fore-and-aft
direction along an inside surface of left side plate 3L of frame 3
in a gap between the inside surface of left side plate 3L and the
traveling power transmission system and the mower-driving power
transmission system, so as to be connected to respective ports 2a
and 2b.
[0093] The laterally extended portions of pipes 23 and 26 are
supported by a clamping stay 60 fixed on rear transaxle housing 1H.
More specifically, rear transaxle housing 1H is formed with a boss
to be attached to frame 3, and clamping stay 60 is fixed onto the
boss.
[0094] Pipes 23 and 26b includes rigid pipes 23b and 26b connected
to ports 1a and 1b, and rigid pipes 23c and 26c connected to ports
2a and 2b, respectively. Rigid pipes 23b, 23c, 26b and 26c are made
of metal, for instance. Flexible hoses 23a and 26a are extended in
the fore-and-aft direction along the inside surface of left side
plate 3L so as to be interposed between rigid pipes 23b and 23c and
between rigid pipes 26b and 26c, respectively. Flexible hoses 23a
and 23b are made of rubber withstanding pressure, for instance.
Rigid pipes 23b and 26b serve as the laterally extended portions of
pipes 23 and 26 connected to first ports 1a and 1b. Rigid pipes 23b
and 26b are connected to flexible hoses 23a and 26a through swivel
joints 54, respectively, and rigid pipes 23c and 26c to flexible
hoses 23a and 26a through swivel joints 55, respectively.
[0095] A hydraulic power steering valve 80 shown in FIG. 2 is
disposed on frame 3 between rear and front transaxles 1 and 2. Rear
transaxle housing 1H is rearwardly outwardly opened by auxiliary
device driving hydraulic fluid supply-and-delivery ports 75 and 76.
A pair of power steering hydraulic pressure fluid pipes 81 and 82
are interposed between ports 75a and 76 and valve 80 along pipes 23
and 26.
[0096] In this embodiment, a reservoir tank 28 is disposed just
behind a rear end surface of frame 3 so as to be fluidly connected
to hydraulic pump P and hydraulic motors M1, M2 and M3. Reservoir
tank 28 is disposed so that a fluid level in reservoir tank 28 is
higher than fluid levels of the fuel sumps in respective transaxle
housings 1H and 2H. Reservoir tank 28 is formed with an upright
cylindrical fluid-supply portion 28a. A breather 42, which also
serves as a fluid-supply opening, is disposed on the top of
fluid-supply portion 28a behind a driver's seat.
[0097] Various sections in vehicle 100 will be more detailed. With
respect to the support of front transaxle 2 by the front portion of
frame 3, as shown in FIGS. 1 to 3, a bracket 4 is fixed on the
front portion of frame 3, and front transaxle housing 2H is
swingably supported by bracket 4 through fore-and-aft horizontal
center pivot 5, so that left and right ends of front transaxle
housing 2H are vertically swingable.
[0098] Left and right axles 6 are extended laterally outward from
rear transaxle housing 1H, and fixed at distal ends thereof to
center portions of unsteerable rear wheels 7, respectively. Left
and right axles 8 are extended laterally outward from front
transaxle housing 2H, and drivingly connected at distal ends
thereof to steerable front wheels 9, respectively.
[0099] Engine 10 is vibro-isolatingly supported on an upper front
portion of frame 3 through vibro-isolating rubbers or the like, and
covered with a bonnet. A steering wheel 12 is disposed upwardly
rearward from the rear end of bonnet 11, and a speed control pedal
13 is disposed at a bottom portion of the rear end of bonnet 11. In
seesaw-like shaped speed control pedal 13, a front portion is
depressed for controlling forward traveling speed of vehicle 100,
and a rear portion is depressed for controlling backward traveling
speed of vehicle 100. A speed control lever 14 pivoted on rear
transaxle housing 1H interlocks with speed control pedal 13. A
brake pedal 41 is disposed in front of speed control pedal 13. A
rear cover 15 is mounted on an upper rear portion of frame 3, and a
driver's seat 16 is disposed on the top of rear cover 15.
[0100] Engine 10 is provided with a downward vertical output shaft
10a. A pulley 10b is fixed on output shaft 10a, and a pulley 10c is
provided on a lower portion of output shaft 10a below pulley 10b
through an electromagnetic clutch 10e. Rear transaxle 1 is provided
with an input shaft 17, which serves as a common pump shaft for
hydraulic pump P and a charge pump 33, projecting upward from rear
transaxle housing 1H. A pulley 17a is fixed on input shaft 17. A
belt is looped over pulleys 10b and 17a so as to constitute the
traveling power transmission system for drivingly connect hydraulic
pump P in rear transaxle 1 to engine 10. A cooling fan 17b is fixed
on input shaft 17 so as to blow cooling wind to rear transaxle
housing 1H.
[0101] As shown in FIG. 3, twin tension pulleys 52 guide an
intermediate portion of belt 18. Either of pulleys 52 has a pivot
extended downward from frame 3. A spring 53 for applying tension is
hooked at one end thereof onto an arm supporting pulleys 52, and
connected at the other end thereof to frame 3.
[0102] As shown in FIG. 1, mower unit 20 incorporating rotary
blades 20a is vertically movably suspended under frame 3 between
front wheels 9 and rear wheels 7. Mower unit 20 is provided at the
top thereof with an input pulley 20b. A mower-driving belt (not
shown) is looped over pulleys 10c and 20b so as to constitute the
mower-driving power transmission system for drivingly connecting
rotary blades 20a in mower unit 20 to engine 10. Electromagnetic
clutch 10e interposed between pulley 10c and engine output shaft
10a is clutched on for transmitting power of engine 10 to mower
unit 20, and clutched off for isolating mower unit 20 from the
power of engine 10.
[0103] Rear transaxle housing 1H incorporates hydraulic pump P and
hydraulic motor MI for driving rear wheels 7 (axles 6), front
transaxle housing 2H incorporates hydraulic motors M2 and M3 for
driving respective front wheels 9 (axles 8), and pipes 23 and 26
are interposed between transaxle housings 1H and 2H, so as to
constitute a hydrostatic transmission (HST) circuit HC1 including
hydraulic pump P and hydraulic motors M1, M2 and M3.
[0104] HST circuit HC1 of vehicle 100 will be described with
reference to FIG. 2. As mentioned above, pipe 23 is interposed
between port 1a of rear transaxle. housing FIH and port 2a of front
transaxle housing 2H, and pipe 26 is interposed between port 1b of
rear transaxle housing 1H and port 2b of front transaxle housing
2H. In rear transaxle housing 1H, a passage 21 is interposed
between hydraulic pump P and hydraulic motor M1, a passage 27 is
interposed between hydraulic pump P and port 1b, and a passage 22
is interposed between hydraulic motor MI and port 1a.
[0105] In rear transaxle housing 2H, fixed displacement hydraulic
motor M2 and variable displacement hydraulic motor M3 are connected
to port 2a through a passage 24 in parallel, and connected to port
2b through a passage 25 in parallel. Passage 24 is bifurcated into
a passage 24a connected to hydraulic motor M2 and a passage 24b to
hydraulic motor M3, and passage 25 is bifurcated into a-passage 25a
connected to hydraulic motor M2 and a passage 25b connected to
hydraulic motor M3.
[0106] In HST circuit having the above structure, hydraulic motor
M1 of rear transaxle 1 and the pair of hydraulic motors M2 and M3
of front transaxle 2 are fluidly connected in series to hydraulic
pump P. Hydraulic motors M2 and M3 in front transaxle 2 are fluidly
connected in parallel with each other to hydraulic pump P so as to
be differentially driven in correspondence to difference of load
between left and right front wheels 9.
[0107] Regarding to circulation route in HST circuit HC1, when
vehicle 100 travels forward, fluid delivered from hydraulic pump P
flows to hydraulic motors M2 and M3 through passage 27, port 1b,
pipe 26, port 2b and passage 25, and then flows to hydraulic motor
M1 through passage 25, port 2a, pipe 23, port 1a and passage 22,
and returns to hydraulic pump P through passage 21. In other words,
when vehicle travels forward, hydraulic pump P supplies fluid to
hydraulic motors M2 and M3 of front transaxle 2 prior to hydraulic
motor M1 of rear transaxle 1. When vehicle 100 travels backward,
fluid flow delivered from hydraulic pump takes a route opposite to
the above route during forward traveling of vehicle 100, so as to
be supplied to hydraulic motor M1 of rear transaxle 1 prior to
hydraulic motors M2 and M3 of front transaxle 2.
[0108] A drive mode switching valve (not shown) for setting vehicle
100 into either a two-wheel drive mode or a four-wheel drive mode
may be interposed between transaxles 1 and 2 across pipes 23 and
26. When the valve is set at the four-wheel drive mode position,
pipes 23 and 26 are entirely passed through the valve between ports
1a and 2a and between 1b and 2b, respectively, thereby circulating
fluid from hydraulic pump P through hydraulic motor M1, M2 and M3.
The valve when set at the two-wheel drive mode position makes a
closed circuit between hydraulic pump P and hydraulic motor M
isolated from ports 2a and 2b, so as to supply fluid from hydraulic
pump P to hydraulic motor M1, thereby driving rear wheels 7 (axles
6), and the valve also makes a closed circuit between hydraulic
motors M2 and M3 independent of the circuit between hydraulic pump
P and hydraulic motor M1, so as to allow circulation of fluid
between hydraulic motors M2 and M3, thereby allowing free
differential rotation of front wheels 9.
[0109] Transaxle housings 1H and 2H are filled with fluid so as to
make respective fluid sumps therein. Rear transaxle housing 1H is
formed with a drain port 1c connected to reservoir tank 28 through
a drainpipe 29. Front transaxle housing 2H is formed with a drain
port 2c connected to reservoir tank 28 through a drainpipe 30.
Therefore, reservoir tank 28 absorbs fluid excessively expanded in
the respective fluid sumps in transaxle housings 1H and 2H.
[0110] Charge pump 33 is disposed in rear transaxle housing 1H so
as to supply fluid to HST circuit HC1, and preferably driven by
input shaft 17 which also serves as the pump shaft of hydraulic
pump P. In rear transaxle housing 1H, a suction line 31 is
interposed between a fluid filter 32 submerged in the fluid sump
and charge pump 33 so as to supply fluid to charge pump 33.
Alternatively, charge pump 33 may suck fluid from reservoir tank 28
disposed outside rear transaxle housing 1H.
[0111] A charge fluid passage 34 is extended from charge pump 33
and bifurcates to be connected to passages 21 and 27 with hydraulic
pump P therebetween. A pair of check valves 36 are disposed on the
bifurcating portions of charge fluid passage 34 connected to
respective passages 21 and 27. Due to this structure, fluid
delivered from charge pump 33 is introduced through corresponding
check valve 36 into one of passages 21 and 27 which is pressurized
lower than the other passage 27 or 21.
[0112] A check valve 39 for preventing cavitation is connected in
parallel with charge pump 33 to suction line 31, and connected to
charge fluid passage 34 between charge check valves 35 through a
later-discussed power steering hydraulic fluid circuit. When one of
pipes 21 and 27 is hydraulically depressed, check valve 39
introduces fluid from suction line 31 to depressed passage 21 or 27
so as to assist the fluid supply from charge pump 33.
[0113] In rear transaxle housing 1H, differential gear unit 38
differentially connects axles 6 to each other, and deceleration
gear train 37 is interposed between a motor shaft of hydraulic
motor M1 and differential gear unit 38. Due to this structure, the
output force of hydraulic motor M1 driven by hydraulic pump P is
transmitted to rear wheels 7 on axles 6 through deceleration gear
train 37 and differential gear unit 38. Variable displacement
hydraulic pump P is provided with a movable swash plate Pa
interlocking with speed control lever 14 (see FIG. 1), which is
pivoted on rear transaxle housing 1H and operatively connected to
speed control pedal 13. Due to the depression amount and direction
of speed control pedal 13, the tilt angle of swash plate Pa is
controlled so as to determine the fluid delivery amount and
direction from hydraulic pump P, thereby determining the rotary
speed and direction of rear wheels 7 (and front wheels 9 in the
four-wheel drive mode).
[0114] A manner of setting peripheral speeds of rear wheels 7 and
front wheels 9 according to the output rotation speed of hydraulic
motor M1 and hydraulic motors M2 and M3, and a mechanism for
setting the peripheral speeds will now be described. In an ordinary
manner, the peripheral speeds of rear wheels 7 and front wheels 9
are set so that the peripheral speed of rear wheels 7 is equal to
the peripheral speed of front wheels 9 when vehicle 100 travels
straight. However, the strict equalization of peripheral speed
between rear wheels 7 and front wheels 9 causes frequent reverse of
large and small peripheral speed relation between rear wheels 7 and
front wheels 9 depending on the ground condition. More
specifically, during traveling of vehicle 100, the state that the
peripheral speed of rear wheels 7 exceeds the peripheral speed of
front wheels 9 (i.e., front wheels 9 rotate following rear wheels
7, because front wheel or wheels 9 are loaded by the ground so that
the peripheral speed of front wheels 9 becomes lower than the
proper peripheral speed thereof corresponding to the set output of
hydraulic motors M2 and M3) alternates with the state that the
peripheral speed of front wheels 9 exceeds the peripheral speed of
rear wheels 7 (i.e., rear wheels 7 rotate following front wheels 9,
because rear wheel or wheels 7 are loaded by the ground so that the
peripheral speed of rear wheels 7 becomes lower than the proper
peripheral speed thereof corresponding to the set output of
hydraulic motor M1). Consequently, vehicle 100 travels in
uncomfortable stiff movement.
[0115] To solve the problem, in present vehicle 100, the output
speeds of hydraulic motor M1 and motors M2 and M3 are set so that
the peripheral speed of rear wheels 7 becomes slightly higher than
the peripheral speed of front wheels 9 during straight traveling of
vehicle 100. In other words, a front assist ratio (a degree of
assisting the rotation of rear wheels 7 by the rotation of front
wheels 9, i.e., a ratio of the set peripheral speed of front wheels
9 to the set peripheral speed of rear wheels 7) is set to be
smaller than 1.0. Consequently, during straight traveling of
vehicle 100, front wheels 9 almost rotate following rear wheels 7.
Even if rear wheel or wheels 7 are loaded and slowed down to some
degree so that the peripheral speed of rear wheels 7 becomes lower
than the proper peripheral speed thereof corresponding to the set
output speed of hydraulic motor M1, the peripheral speed of rear
wheels 7 is still higher than or equal to the peripheral speed of
front wheels 9, i.e., the state that the rotation of rear wheels 7
assists the rotation of front wheels 9 is still maintained. In
other words, during straight traveling of vehicle 100 with
hydraulic motors M1, M2 and M3 set as the above, it rarely occurs
that the peripheral speed of front wheels 9 abnormally exceeds the
peripheral speed of rear wheels 7. Therefore, vehicle 100 can
comfortably travel without stiff movement.
[0116] However, due to the output rotary speed setting of hydraulic
motors M1, M2 and M3 for making the peripheral speed of rear wheels
7 exceed the peripheral speed of front wheels 9, the rotation of
front wheels 9 follows the rotation of rear wheels 7 so as to cause
a counter driving force from axles 8 to hydraulic motors M2 and M3,
whereby hydraulic motors M2 and M3 act as pumps so as to
hydraulically depress the suction ports of motors M2 and M3,
thereby causing cavitation in HST circuit HC1 and causing hunting
of vehicle 100. This phenomenon remarkably occurs when vehicle 100
turns, especially sharply turns.
[0117] To solve the problem, a check valve is connected to a
portion of HST circuit HC1, which serves as a suction part of
hydraulic motors M2 and M3 (the series of passages 22, 23 and 24
(24a and 24b) between hydraulic motor M1 and the pair of hydraulic
motors M2 and M3 during forward traveling of vehicle 100, or the
series of passages 21, 27, 26 and 25 (25a and 25b ) between
hydraulic motor M1 and the pair of hydraulic motors M2 and M3
through hydraulic pump P during backward traveling of vehicle 100),
so as to supply fluid into HST circuit HC1 from the outside of HST
circuit HC1. In the embodiment of FIG. 2, a check valve 40 is
disposed in front transaxle 2 so as to introduce fluid from the
fluid sump in front transaxle housing 2H into the suction part of
hydraulic motors M2 and M3 during forward traveling of vehicle 100,
and a check valve 39 is disposed in rear transaxle 1 so as to
introduce fluid from the fluid sump in rear transaxle housing 1H
into the suction part of hydraulic motors M2 and M3 during backward
traveling of vehicle 100.
[0118] Incidentally, as mentioned above, during forward traveling
of vehicle 100, in vehicle 100, fluid is supplied to front
hydraulic motors M2 and M3 prior to rear hydraulic motor M1. This
fluid circulation route is advantageous for forward descending a
slope. When vehicle 100 travels forward on a downhill, the weight
of vehicle 100 applied on front wheels 9 is larger than that
applied on rear wheels 7, so that power required for driving front
wheels 9 is larger than that for driving rear wheels 7. The fluid
circulation route smoothens forward traveling of vehicle 100 on a
downhill.
[0119] However, when vehicle 100 travels forward on an uphill, the
weight of vehicle 100 applied on rear wheels 7 is larger than that
applied on front wheels 9, so that power required for driving rear
wheels 7 is larger than that for driving front wheels 9. To
correspond to this case, alternatively, the fluid circulation route
may be reversed so as to supply fluid to rear hydraulic motor M1
prior to front hydraulic motors M2 and M3, thereby smoothening
forward traveling of vehicle 100 on an uphill.
[0120] Vehicle 100 can be equipped with various working devices,
such as a front blade, a front snowplow, a rear tiller and a plow,
as well as mower unit 20. The diameter ratio between front tires
and rear tires varies according to the weight and position of the
working device equipped on vehicle 100. The variation of diameter
ratio means variation of the front assist ratio. Vehicle 100 is
provided on front transaxle 2 with an adjustable cam mechanism CM
for setting the front assist ratio into a range between 0.7 and 1.0
in correspondence to the target working device.
[0121] Cam mechanism CM will now be described with reference to
FIGS. 8 and others. Cam mechanism CM is disposed on the rear
portion of front transaxle 2. When steering wheel 12 is rotated
from a neutral position (straight traveling position), a piston rod
90 of a power steering cylinder 79 is telescoped through the
later-discussed power steering hydraulic circuit. The movement of
piston rod 90 is transmitted to a left front wheel support unit 48L
so as to laterally turn left front wheel 9 with left front wheel
support unit 48L. The lateral turn of left front wheel 9 is
transmitted to a right front wheel support unit 48R through a tie
rod 49 so as to laterally turn right front wheel 9 with right front
wheel support unit 48R in the same direction with left front wheel
9. The lateral turn of right front wheel support unit 48R is
transmitted to cam mechanism CM through a control link 46. Cam
mechanism CM comprises: a control lever 45 pivotally connected to
control link 46 through a pin 47; a control arm 43; and a swash
plate pivot shaft M3b serving as a rotary axis of a movable swash
plate M3a of hydraulic motor M3. Cam mechanism CM converts the
movement of control link 46 into rotational movement of swash plate
pivot shaft M3b so as to tilt swash plate M3a at a target angle for
reducing the displacement of hydraulic motor M3, thereby
accelerating front wheels 9 during turning of vehicle 100.
[0122] Control arm 43 is fixed at one end thereof onto a portion of
swash plate pivot shaft M3b projecting rearward from front
transaxle housing 2H so as to be rotatable integrally with swash
plate M3a. Control arm 43 is provided on the other end portion
thereof with a contact plate 44 abutting against control lever 45.
Contact plate 44 is formed with two slots through which respective
adjusting bolts 44a are screwed into control arm 43. By loosening
bolts 44a, the position of contact plate 44 can be adjusted so as
to adjust the initial tilt angle of swash plate M3a (during
straight traveling of vehicle 100), i.e., adjust the front assist
ratio. As mentioned above, by this adjustment, the front assist
ratio is set within the range between 0.7 and 1.0 in correspondence
to the working device equipped onto vehicle 100.
[0123] Pin 47 is disposed behind front transaxle housing 2H, and
the end of control link 46 is pivotally provided on pin 47 between
the rear end surface of front transaxle housing 2H and control
lever 45, i.e., in front of control lever 45. A pivot shaft of
control lever 45 coaxially engages to pin 47, thereby pivotally
connecting control lever 45 to control link 46. Due to this
arrangement, control link 46 is disposed forward as far as
possible, i.e., control link 46 extremely approaches the rear
surface of front transaxle 2H, so as to reduce the fore-and-aft
width of front transaxle 2 with cam mechanism CM.
[0124] A hydraulic piping construction in vehicle 100 will be
described. To minimize a vehicle, hydraulic pressure fluid pipes
are requested to be collected inside a vehicle frame. In working
vehicle 100, front transaxle 2 incorporates left fixed displacement
hydraulic motor M2 and right variable displacement hydraulic motor
M3, as mentioned above. Therefore, cam mechanism CM for controlling
swash plate M3a of hydraulic motor M3 is disposed eccentrically
rightward on the rear portion of front transaxle 2, as shown in
FIG. 8. Transaxle housing 2H projects rearward at the left portion
thereof laterally opposite to cam mechanism CM so as to have the
pair of leftwardly opened ports 2a and 2b.
[0125] On the other hand, rightwardly opened ports 1a and 1b of
rear transaxle 1 are disposed at the right side surface of rear
transaxle housing 1H. This arrangement of ports 1a and 1b and ports
2a and 2b requires pipes 23 and 26 to be disposed rightward from
ports 1a and 1b at the right rear portion of vehicle 100, and to be
disposed leftward of the front portion of vehicle 100 so as to be
connected to ports 2a and 2b. However, the traveling power
transmission system and the mower-driving power transmission system
occupy a main space inside frame 3. Further, mower unit 20 is
disposed under the middle portion of frame 3. Consequently, the
space for arranging pipes 23 and 26 between the front and rear
portions of vehicle 100 without interfering with the power
transmission systems and mower unit 20 is limited.
[0126] Other required things in arrangement of pipes are that the
piping work requires no other device to be removed, and that work
for attaching another device requires no pipe to be removed.
Further, to reduce internal pressure resistance in pipes, the pipes
include few bent portions as much as possible, and rigid pipes such
as steel pipes are desired to serve as the hydraulic pressure fluid
pipes. On the other hand, prevention of excessive twist and folding
of the pipes caused by the swing of front transaxle 2 around center
pivot 5, and prevention of ends of pipes connected to ports from
having fluid leak and from being damaged are requested.
[0127] Arrangement of pipes in vehicle 100 solving these problems
will be described. In this regard, referring to FIGS. 1 and 3,
extension routes of pipes 23 and 26 from ports 1a and 1b on rear
transaxle housing 1H will be described. Rear rigid pipes 23b and
26b of pipes 23 and 26 are extended rightward from ports 1a and 1b,
bent, extended upwardly forward, bent again, and extended leftward
just in front of the front end surface of rear transaxle housing
1H. Clamping stay 60 fixed on housing 1H clamps the laterally
(leftward) extended intermediate portions of rear rigid pipes 23b
and 26b. As shown in FIG. 4(a), clamping stay 60 is fixed on a
mount boss 70 formed on housing 1H. Mount boss 70 is used for
attaching rear transaxle 1 onto a frame of another type vehicle.
Arrangement of clamping stay 60 will be detailed later.
[0128] Rear rigid pipes 23b and 26b extended leftward just in front
of rear transaxle housing 1H are bent at the left portions thereof,
extended vertically upward, bent again, and extended horizontally
forward along the bottom edge of left side plate 3L when viewed in
side as shown in FIG. 1, and along the inside surface of left side
plate 3L when viewed in plan as shown in FIG. 3. A clamping stay 61
is fixed onto left side plate 3L so as to clamp the horizontally
forward extended portions of rear rigid pipes 23b and 26b.
[0129] Rear rigid pipes 23b and 26b are swivellably connected to
respective rear ends of flexible hoses 23a and 26a through
respective swivel joints 54 in front of clamping stay 61. Flexible
hoses 23a and 26a are extended substantially horizontally forward,
i.e., substantially coaxially to rear rigid pipes 23b and 26b,
along the bottom edge of left side plate 3L when viewed in side as
shown in FIG. 1, and along the inside surface of left side plate 3L
when viewed in plan as shown in FIG. 3. Flexible hoses 23a and 26a
are connected at front ends thereof to respective rear ends of
front rigid pipes 23c and 26c through respective swivel joints 55
adjacent to a front portion of left side plate 3L. Front rigid
pipes 23c and 26c are extended horizontally forward from respective
swivel joints 55, bent and extended leftwardly downward just behind
front transaxle 2 so as to be connected to respective ports 2a and
2b on front transaxle housing 2H.
[0130] Due to this arrangement, the whole pipes 23 and 26 between
ports 1a and 1b and ports 2a and 2b are prevented from interfering
with another device or member. In this regard, the fore-and-aft
extended main portions of pipes 23 and 26 (including flexible hoses
23a and 26a) are disposed along the bottom edge of left side plate
3L when viewed in side, higher than mower unit 20, thereby being
prevented from interfering with mower unit 20. Also, the
fore-and-aft extended main portions of pipes 23 and 26 (including
flexible hoses 23a and 26a) are disposed along the inside surface
of left side plate 3L when viewed in plan, leftward from the
traveling power transmission system, including pulley 10b and belt
18, the mower-driving power transmission system, including pulley
20b and the mower-driving belt, and the operation link mechanisms
interlocking with speed control pedal 13 and brake pedal 41.
[0131] Rigid pipes 23b, 23c, 26b and 26b can be diametrically large
so as to reduce the internal pressure resistance therein. Further,
all the bent portions of pipes 23 and 26 are provided on rigid
portions rigid pipes 23b, 23c, 26b and 26b, and the number of bent
portions are reduced as much as possible. Flexible hoses 23a and
26a are disposed along left side plate 3L so as to absorb the
deflection of pipes 23 and 26 caused by the swing of front
transaxle 2 around center pivot 5. Consequently, pipes 23 and 26
are prevented from being unexpectedly bent or being broken at ends
thereof connected to ports 1a, 1b, 2a and 2b.
[0132] Due to the clamping of rear rigid pipes 23b and 26b by
clamping stays 60 and 61, ends of rigid pipes 23b and 26b connected
to ports 1a and 1b are prevented from receiving excessive bending
force, shearing force, and stretching force, and thereby being
prevented from having fluid leak or being damaged. Further, swivel
joints 54 and 55 absorb twist of pipes 23 and 26 caused by the
swing of front transaxle 2 around center pivot 5 so as to prevent
pipes 23 and 26 from being damaged or deformed caused by the
twist.
[0133] The power steering hydraulic circuit system and associate
piping in vehicle 100 will be described with reference to FIG. 2.
In vehicle 100, power steering cylinder 79 is supplied with fluid
from charge pump 33. The pair of auxiliary device driving hydraulic
fluid supply-and-delivery ports 75 and 76 are disposed on rear
transaxle housing 1H. In rear transaxle housing 1H, charge pump 33
is connected through a passage 98 to port 75, and through a passage
99 to port 76. Hydraulic power steering valve 80 is provided with a
pair of ports 85 and 86 corresponding to respective ports 75 and
76. At the outside of rear transaxle housing 1H, pipe 81 is
interposed between ports 75 and 85, and pipe 82 is interposed
between ports 76 and 86. Hydraulic power steering valve 80 is also
provided with a pair of ports 87 and 88 corresponding to front and
rear ports of power steering cylinder 79. A hydraulic pressure
fluid pipe 83 is interposed between port 87 and the front port of
power steering cylinder 79, and a hydraulic pressure fluid pipe 84
is interposed between port 88 and the rear port of power steering
cylinder 79.
[0134] In the above hydraulic circuit system, valve 80 is switched
correspondence to the rotation angle and direction of steering
wheel 12, so as to control fluid-supply from charge pump 33 to
power steering cylinder 79.
[0135] A relief valve 50 is interposed between pipes 98 and 99.
When higher-pressurized pipe 98 is excessively pressurized, relief
valve 50 is opened so as to bypass excessive pressure fluid from
higher-pressurized pipe 98 to lower-pressurized pipe 99 so as to
regulate the hydraulic pressure in the power steering hydraulic
circuit system. In rear transaxle housing 1H, the recovery fluid
flowing in pipe 82 joins the excessive pressure fluid released from
relief valve 50 so as to be charged to HST circuit HC1.
[0136] Referring to arrangement of power steering hydraulic
pressure fluid pipes 81 and 82, as shown in FIG. 1, ports 75 and 76
are juxtaposed behind ports la and 1b on the right side surface of
rear transaxle housing 1H. Pipes 81 and 82 are extended from
respective ports 75 and 76 along pipes 23 and 26, as partly shown
in FIGS. 1 and 3, i.e., in a course similar to the course of pipes
23 and 26, so that the forwardly extended main portions of pipes 75
and 76 are extended along the inside surface of left side plate 3L
when viewed in plan. Pipes 75 and 76 are bent at front ends of the
forwardly extended portions thereof behind valve 80, extended
upward, bent again and extended rightward above belt 18 so as to be
connected to ports 85 and 86 of valve 80.
[0137] In this way, the portions of pipes 81 and 82 from the rear
ends thereof connected to ports 75 and 76 to the front ends of the
forwardly extended portions thereof are disposed along pipes 23 and
26 prevented from interfering with the traveling power transmission
system, the mower-driving power transmission system and mower unit
20. Further, all the fore-and-aft extended main portions of pipes
23 and 26 and pipes 81 and 82 are compactly collected along left
side plate 3L.
[0138] As shown in FIG. 3, power steering cylinder 79 is fixed onto
frame 3 so as to be disposed along the outside surface of left side
plate 3L. Piston rod 90 of power steering cylinder 79 is pivotally
connected at the front end thereof to a bracket 48a extended from
the top of left front wheel support unit 48L, so as to be prevented
from interfering with cam mechanism CM disposed rightward on rear
transaxle 2 and connected to right front wheel support unit 48R.
Piston rod 90 is telescoped according to operating steering wheel
12, so as to leftwardly or rightwardly turn left and right front
wheels 9 together with left and right front wheel support units 48L
and 48R.
[0139] Clamping stays 60 and 61 for clamping pipes 23 and 26 will
be described with reference to FIGS. 4(a) and 4(b). Referring to
FIG. 4(a), clamping stay 60 comprises a main stay member 66 and a
keep plate 67. Main stay member 66 includes a tab portion fastened
to mount boss 70 of rear transaxle housing 1H through a bolt 71.
Main stay member 66 also includes a pipe support portion for
supporting rear rigid pipes 23b and 26b of pipes 23 and 26. The
pipe support portion is formed with a pair of sectionally
semicircular grooves into which rear rigid pipes 23b and 26b are
fitted. Keep plate portion 67 is fastened to the pipe support
portion of main stay member 66 through bolts 72, whereby rear rigid
pipes 23b and 26b are clamped between main stay member 66 and keep
plate portion 67. Incidentally, a shock absorbing rubber 66a is
fitted between stay member 66 and keep plate portion 67 so as to be
wound around pipe portions 23b and 26b, thereby preventing noise
from a gap between rigid pipes 23b and 26b and clamping stay
60.
[0140] In this way, clamping stay 60 is fixed on rear transaxle
housing 1H so as to clamp the laterally extended portions of rigid
pipes 23b and 26b. In the embodiment shown in FIG. 1 and 4(a),
clamping stay 60 is disposed so as to vertically align the
laterally extended portions of rigid pipes 23b and 26b.
Alternatively, clamping stay 60 may be disposed onto rear transaxle
housing 1H so as to horizontally align the laterally extended
portions of rigid pipes 23b and 26b.
[0141] Referring to FIG. 4(b), clamping stay 61 comprises a main
stay member 68 and a keep plate 69. Main stay member 68 includes a
tab portion fastened to frame 3, more specifically, side plate 3L
or 3R (in this embodiment, left side plate 3L), through a bolt 73.
Main stay member 68 also includes a pipe support portion for
supporting rear rigid pipes 23b and 26b of pipes 23 and 26. The
pipe support portion is formed with a pair of sectionally
semicircular grooves into which rear rigid pipes 23b and 26b are
fitted. Keep plate portion 69 is fastened to the pipe support
portion of main stay member 68 through bolts 74, whereby rear rigid
pipes 23b and 26b are clamped between main stay member 68 and keep
plate portion 69. Incidentally, a shock absorbing rubber 68a is
fitted between stay member 68 and keep plate portion 69 so as to be
wound around pipe portions 23b and 26b, thereby preventing noise
from a gap between rigid pipes 23b and 26b and clamping stay
61.
[0142] In this way, clamping stay 61 is fixed onto left side plate
rear transaxle housing 1H so as to clamp the fore-and-aft extended
portions of rigid pipes 23b and 26b. In the embodiment shown in
FIG. 1 and 4(b), clamping stay 61 is disposed so as to vertically
align the fore-and-aft extended portions of rigid pipes 23b and
26b. Alternatively, clamping stay 61 may be disposed onto rear
transaxle housing 1H so as to horizontally align the fore-and-aft
extended portions of rigid pipes 23b and 26b.
[0143] The above-mentioned arrangement of pipes 23 and 26 is
associated with the rightwardly outward opened ports 1a and 1b on
the right side of rear transaxle 1. Alternatively, referring to
FIG. 5, ports 1a and 1b are opened leftwardly outward on the left
side of rear transaxle 1, i.e., on the same lateral side of vehicle
100 with ports 2a and 2b of front transaxle 2. In this regard, rear
rigid pipes 23b and 26b are bent upwardly forward from rear ends
thereof connected to ports 1a and 1b of rear transaxle 1, and bent
again so as to be extended horizontally forward along left side
plate 3L (along the bottom edge of left side plate 3L when viewed
in side, and along the inside surface of left side plate 3L when
viewed in plan). The arrangement of pipes 23 and 26 between swivel
joints 54 and ports 2a and 2b is similar to the arrangement when
ports 1a and 1b are disposed on the right side of rear transaxle
1.
[0144] Further alternatively, referring to FIG. 6, a port block PB
is fixed onto the right side surface of rear transaxle housing 1H.
Port block PB is bored with L-like shaped end portions of passages
22, 27, 98 and 99 (see FIG. 2). Ports 1a and 1b at front ends of
respective passages 22 and 27, and ports 75 and 76 at front ends of
respective passages 98 and 99 are forwardly outward opened on the
front end surface of port block PB. The space within port block PB
required for rightward-to-forward course change of passages 22, 27,
98 and 99 is smaller than the space required for
rightward-to-forward course change of external pipes 23 (23b), 26
(26b), 81 and 82, i.e., for curving or bending the external pipes.
Therefore, port block PB provided with ports 1a, 1b, 75 and 76 on
the front end surface thereof is available for arranging pipes 23
and 26 (and 81 and 82) inside frame 3 in vehicle 100 having a very
narrow gap between rear transaxle housing 1H and right side plate
3R of frame 3, because, if pipes 23 and 26 are connected to ports
1a and 1b without port block PB in the condition that the gap
between rear transaxle housing 1H and right side plate 3R is very
narrow, pipes 23 and 26 extended rightward from ports 1a and 1b
cannot be curved forward within the very narrow gap between rear
transaxle housing l H and right side plate 3R (i.e., pipes 23b and
26b cannot help projecting rightward from right side plate 3R of
frame 3 to be curved forward).
[0145] Alternatively, referring to FIG. 7, port block PB bored with
L-like shaped end portions of passages 22, 27, 98 and 99 is fixed
onto the left side surface of rear transaxle housing 1H, so as to
provide forwardly outward opened ports 1a, 1b, 75 and 76 at the
left side of rear transaxle 1. Incidentally, the structure in the
front portion of vehicle 100 which is omitted in each of FIGS. 5 to
7 is the same as that shown in FIGS. 1 and 3.
[0146] Arrangement of reservoir tank 28 in vehicle 100 will be
described. In vehicle 100 shown in FIGS. 1 and 3 (also in the cases
of FIGS. 5, 6 and 7), reservoir tank 28 is disposed just behind the
rear end surface of frame 3, and disposed in rear cover 15, so that
the fluid level in reservoir tank 28 is higher than the fluid
levels of the respective fluid sumps in front and rear transaxle
housings 1H and 2H. Reservoir tank 28 is fluidly connected to front
and rear transaxles 1 and 2 through respective drain pipes 29 and
30 so as to absorb excessive fluid from front and rear transaxle
housings 1H and 2H.
[0147] The arrangement of reservoir tank 28 behind the rear end
surface of frame 3 is available for works of attachment, detachment
and maintenance of reservoir tank 28, because reservoir tank 28
disposed at this position comes behind tires of rear wheels 7, and
does not require rear wheels 7 to be detached for the works. During
traveling of vehicle 100, the defect of reservoir tank 28 yielded
to stones or mud spattered or knocked by the tires of rear wheel 7
becomes fewer.
[0148] Reservoir tank 28 is disposed upright (vertically long) so
as to heighten the fluid level therein. Even if vehicle 100 travels
on a slope, the high fluid level in reservoir tank 28 prevents the
fluid sump in front and rear transaxle housings 1H and 2H from
being contaminated with air bubbles, thereby preventing fluid
circulating among hydraulic pump P and hydraulic motors M1, M2 and
M3 from being contaminated with air bubbles. The vertical length of
upright reservoir tank 28 is sufficient to prevent the fluid level
surface from touching the bottom surface of reservoir tank 28
regardless of the swing of front transaxle 2 around center pivot
5.
[0149] Another advantage of reservoir tank 28 disposed behind the
rear end surface of frame 3 is to provide a sufficient length of
drainpipe 30 between front transaxle 2 and reservoir tank 28 so as
to correspond to the swing of front transaxle 2 around center pivot
5.
[0150] Rear cover 15 is provided at a top portion thereof behind
driver's seat 16 with a hole, through which upright cylindrical
fluid-supply portion 28a of reservoir tank 28 projects upwardly
outward. Breather 42, serving as the fluid-supply opening of
reservoir tank 28, is disposed on the top of fluid-supply portion
28a above the top of rear cover 15, thereby facilitate fuel-supply
work by a driver on seat 16. Further, due to such a high position
of breather 42 (i.e., the fluid-supply opening of reservoir tank
28), fuel is prevented from overflowing from breather 42 even when
vehicle 100 travels on a slope.
[0151] Alternatively, referring to FIG. 9, pipes 23 and 26 comprise
flexible hoses (such as pressure rubber hoses) 23d and 26d and
rigid pipes (such as metal or steel pipes) 23e and 26e. Flexible
hoses 23d and 26d are connected to respective ports 2a and 2b of
front transaxle 2. Rigid pipes 23e and 26e include the fore-and-aft
main portion of pipes 23 and 26 and are connected to ports 1a and
1b of rear transaxle 1.
[0152] Rigid pipes 23e and 26e include the same arrangement of
rigid pipes 23b and 26b. In this regard, rigid pipes 23e and 26e
connected to ports 1a and 1b includes laterally extended portions,
which are disposed just in front of rear transaxle housing 1H and
clamped by clamping stay 60 fixed on mount boss 70 of rear
transaxle housing 1H. The fore-and-aft extended main portions of
rigid pipes 23e and 26e are extended along left side plate 3L
(along the bottom edge of left side plate 3L when viewed in side,
and along the inside surface of left side plate 3L when viewed in
plan), so as to replace the fore-and-aft extended front portions of
rigid pipes 23b and 26b and flexible hoses 23a and 26a. Rigid pipes
23e and 26e are connected at front ends thereof to respective
flexible hoses 26d and 26e through respective swivel joints 55. The
fore-and-aft extended main portions of rigid pipes 23e and 26e are
clamped by a clamping stay 63 fixed onto left side plate 3L just
behind swivel joints 55.
[0153] Vehicle 100 shown in FIG. 9 may be provided with any of
other arrangements of ports 1a and 1b on rear transaxle 1 shown in
FIGS. 5, 6 and 7. In this case, rigid pipes 23e and 26e are
rearranged to suit the arrangement of ports 1a and 1b.
[0154] Flexible hoses 23d and 26d are extended forward from swivel
joints 55 and bent rightwardly downward just behind of rear
transaxle 2 so as to be connected to ports 2a and 2b on the rear
end of rear transaxle housing 2H.
[0155] The arrangement of pipes 23 and 26 shown in FIG. 9 has the
same advantages with the arrangement of pipes 23 and 26 shown in
FIGS. 1 and 3, and additionally, has an advantage in reduction of
flexible pipe portions, which are diametrically smaller than rigid
pipe portions and have large internal pressure resistance. Namely,
the reduction of flexible pipe portions leads to reduction of
internal pressure resistance in pipes 23 and 26.
[0156] Referring to FIG. 1, a pair of left and right mower hangers
91 are disposed in front of front transaxle 2. Mower hangers 91 are
extended downward from bottoms of respective side plates 3L and 3R
just in front of front transaxle 2, and bent to be extended
rearwardly downward under front transaxle 2. Left and right link
rods 91a are pivotally connected at front ends thereof onto rear
ends of respective mower hangers 91, and extended rearwardly
downward so as to be pivotally connected at rear ends thereof to
respective front hooks of mower unit 20. Therefore, mower unit 20
can be tilted in the fore-and-aft direction relative to vehicle
106, so as to fit the ground during traveling of vehicle 100.
[0157] To ensure a proper performance of link rods 91a serving as a
parallel linkage, location of mower hangers 91 is important.
Conventional mower hangers disposed behind front transaxle 2 are
troublesome to be attached or detached to and from frame 3 or to be
reformed. In the present vehicle 100, mower hangers 91 disposed in
front of front transaxle 2 can be easily and efficiently attached
to frame 3 while adjusting its vertical and fore-and-aft position.
Further, due to the arrangement of mower hangers 91 in front of
front transaxle 2, front transaxle 2 is shifted rearward from its
conventional position so as to shorten the gap between rear wheel
axles 6 and front wheel axles 8, thereby reducing the turning
radius of vehicle 100.
[0158] Incidentally, engine 10 is provided with a muffler 10d
disposed on a front end portion of frame 3 in front of front
transaxle 2. Frame 3 is integrally formed with a muffler cover 3a
covering a front surface of muffler 10d. Muffler cover 3a serves as
a part of a bumper of vehicle 100.
[0159] Structure of rear transaxle 1 will be described with
reference to FIGS. 16 to 24. As shown in FIG. 16, main ports 1a and
1b and auxiliary ports 75 and 76 are juxtaposed on the same (right)
side surface of housing 1H, thereby compactly collecting
axle-driving hydraulic pressure fluid pipes 23 and 26 and power
steering hydraulic pressure fluid pipes 81 and 82 so as to be
connected to these ports.
[0160] As mentioned above, in rear transaxle housing 1H are
disposed hydraulic pump P and charge pump 33, which are driven by
power from engine 10 through the traveling power transmission
system disposed out of rear transaxle 1, hydraulic motor M1 fluidly
connected to hydraulic pump P, and axles 6 driven by hydraulic
motor M1. Also, in rear transaxle housing 1H are disposed passage
21 interposed between hydraulic pump P and port 1a, passage 27
interposed between hydraulic motor M1 and port 1b, passage 98
interposed between charge pump 33 and port 75, and passage 99
interposed (through either of charge check valves 35) between the
suction (lower-pressurized) side of hydraulic pump P (i.e., either
of passages 21 and 27) and port 76 (see FIG. 2).
[0161] Further, in rear transaxle housing 1H is disposed a center
section 101 interposed between hydraulic pump P and hydraulic motor
M1. Center section 101 is formed with a pair of pump kidney ports
57a and 57b opened to hydraulic pump P, and with a pair of motor
kidney ports 56a and 56b opened to hydraulic motor M1. Passage 21
fluidly connecting hydraulic pump P and hydraulic motor M1 to each
other is bored within center section 101 so as to be interposed
between kidney ports 57a and 56a. A part of passage 22 interposed
between hydraulic pump P and port 1a is bored within center section
101 so as to be connected to kidney port 57b. A part of passage 27
interposed between hydraulic motor M1 and port 1b is bored within
center section 101 so as to be connected to kidney port 56b.
[0162] In rear transaxle housing 1H is also disposed a charge pump
casing 102 joined to center section 101. Charge pump casing 102
incorporates charge pump 33 and is formed therein with a part of
passage 98 to be connected to port 75, and a part of passage 99 to
be connected port 76. Charge pump casing 102 is also formed therein
with a part of passage 22 interposed between hydraulic pump P and
port 1a, and a part of passage 27 interposed between hydraulic
motor M1 and port 1b. The parts of passages 22 and 27 within charge
pump casing 102 continue to the respective parts of passages 22 and
27 within center section 101 so as to be connected to respective
kidney ports 57b and 56b.
[0163] Referring to FIG. 17, the inner space of rear transaxle
housing 1H is partitioned by a partition wall between a hydraulic
circuit chamber and a transmission gear chamber. Hydraulic pump P
and motor M1 are disposed in the hydraulic circuit chamber, and
deceleration gear train 37, differential gear unit 38 and axles 6
are disposed in the transmission gear chamber. As shown in FIGS. 16
and 23, rear transaxle housing 1H is constituted by upper and lower
halves joined to each other through bolts 153.
[0164] Referring to FIG. 21, as mentioned above, the upper portion
of input shaft 17 projecting vertically upward from rear transaxle
housing 1H is fixedly provided thereon with input pulley 17a so as
to be drivingly connected to engine 10 through belt 18, and is
fixedly provided thereon with cooling fan 17b for cooling rear
transaxle housing 1H under pulley 17a. In rear transaxle housing
1H, vertical input pulley 17 serves as the rotary axial shaft of
hydraulic pump P.
[0165] Variable displacement hydraulic pump P, having input shaft
17 serving as the vertical rotary axis thereof, is vertically
mounted onto a rear top surface of center section 101 at which
kidney ports 57a and 57b are opened. Fixed displacement hydraulic
motor M1, having a laterally (leftward) horizontal motor shaft 127
serving as the rotary axis thereof, is mounted onto a front left
side surface of center section 101 at which kidney ports 56a and
56b are opened, so as to be fluidly connected to hydraulic pump P.
Motor shaft 127 is drivingly connected to deceleration gear train
37 so as to transmit the output force of hydraulic motor M1 to
axles 6 through deceleration gear train 37 and differential gear
unit 38.
[0166] As shown in FIG. 23, vertical input shaft 17 penetrates
center section 101 and is inserted into charge pump casing 102
attached to the bottom surface of center section 101 so as to serve
as the drive shaft of charge pump 33 in charge pump casing 102.
Charge pump 33 sucks fluid from the fluid sump in rear transaxle
housing 1H so as to supply fluid to the axle-driving hydraulic
circuit, and to the auxiliary device (power steering) driving
hydraulic circuit through ports 75 and 76.
[0167] As shown in FIGS. 16 and 21, speed control lever 14
operatively connected to speed control pedal 13 is pivoted on rear
transaxle housing 1H so as to control the tilt angle and direction
of swash plate Pa of hydraulic pump P.
[0168] The structure of the hydraulic circuit system in rear
transaxle 1 will be more detailed. As shown in FIGS. 17 and 24(b),
center section 101 is fastened to an inside wall of rear transaxle
housing 1H through bolts 151. As shown in FIG. 17, the circular
rear top surface of center section 101, onto which hydraulic pump P
is mounted, serves as a pump contact surface 103. In pump contact
surface 103, right pump kidney port 57a and left pump kidney port
57b are laterally symmetrically opened upward, and a vertical shaft
hole 17n, into which input shaft 17 is rotatably inserted, is
opened upward between right and left pump kidney ports 57a and 57b.
Vertical shaft hole 17n is passed through center section 101 and
also opened downward at the bottom surface of center section
101.
[0169] As shown in FIG. 21, a cylinder block 104 of hydraulic pump
P is slidably rotatably fitted onto pump contact surface 103 so as
to open cylinder holes therein to pump kidney ports 57a and 57b,
and is not-relatively rotatably fitted on input shaft 17 passed
through shaft hole 17n (in a spline-engaging manner). Pistons 109
are reciprocally slidably fitted in the respective cylinder holes
of cylinder block 104, and project at heads thereof outward from
cylinder block 104 so as to abut against movable swash plate Pa.
Input shaft 17 projects upward from cylinder block 104, freely
penetrates movable swash plate Pa, and projects upward from the top
wall of rear transaxle housing 1H so as to be fixedly provided
thereon with pulley 17a and cooling fan 17b, as mentioned above.
Input shaft 17 inserted in shaft hole 17n also projects downward
from center section 101 into charge pump casing 102 so as to serve
as the drive shaft of charge pump 33.
[0170] Referring to FIGS. 17, 18 and 20, a fore-and-aft horizontal
passage hole 21, serving as passage 21 interposed between hydraulic
pump P and motor M1, is bored in center section 101, so as to be
connected at a rear upper end portion to right pump kidney ports
57a, and at a front upper end portion thereof to rear motor kidney
port 56a. The part of passage 27 bored in center section 101
comprises fluid passage holes 27c, 27d and 27e, and the part of
passage 27 bored in charge pump casing 102 is a fluid passage hole
27b. Fluid passage hole 27e is extended rightwardly downward from
left pump kidney port 27b to a fore-and-aft intermediate portion of
fluid passage hole 27d. Fluid passage hole 27d is fore-and-aft
horizontally extended under fluid passage hole 21 in parallel, and
connected at a front end portion thereof to vertical fluid passage
hole 27c. Fluid passage hole 27c is opened downward at the bottom
surface of center section 101 so as to be directly coaxially
connected to vertical fluid passage hole 27b bored in charge pump
casing 102.
[0171] As shown in FIG. 23, the circular front left side surface of
center section 101, onto which hydraulic motor M1 is mounted,
serves as a motor contact surface 129. In motor contact surface
129, rear motor kidney port 56a and front motor kidney port 56b are
symmetrically opened leftward, and a lateral horizontal shaft hole
127a, into which motor shaft 127 is rotatably inserted, is opened
leftward between rear and front motor kidney ports 56a and 56b.
[0172] As shown in FIG. 17, a cylinder block 120 of hydraulic motor
M1 is slidably rotatably fitted onto motor contact surface 129 so
as to open cylinder holes therein to motor kidney ports 56a and
56b, and is not-relatively rotatably fitted on motor shaft 127
inserted in shaft hole 127a (in a spline-engaging manner). Pistons
123 are reciprocally slidably fitted in the respective cylinder
holes of cylinder block 120, and project at-heads thereof outward
from cylinder block 120 so as to abut against a fixed swash plate
M1a.
[0173] As shown in FIG. 17, motor shaft 127, rotatably fitted at a
right end portion thereof in shaft hole 127a of center section 101,
is journalled through a bearing 128 by the partition wall between
the hydraulic circuit chamber and the transmission gear chamber,
and extended at a left end portion thereof into the transmission
gear chamber so as to be provided thereon with a gear 127b and a
brake disc 140.
[0174] Referring to FIGS. 17 and 18, rear motor kidney port 56a is
connected to right pump kidney port 5 7a through horizontal fluid
passage hole (passage) 21, as mentioned above. Referring to FIGS.
18 and 24(b), the part of passage 22 bored in center section 101
comprises fluid passage holes 22c and 22d, and the part of passage
22 bored in charge pump casing 102 is a fluid passage hole 22b.
Fluid passage hole 22d is fore-and-aft horizontally extended in a
front portion of center section 101, and connected at an upper
portion thereof to front motor kidney port 56b. Vertical fluid
passage hole 22c is extended from fluid passage hole 22d, and
opened downward at the bottom surface of center section 101 just in
front of fluid passage hole 27c, so as to be directly coaxially to
vertical fluid passage hole 22b bored in charge pump casing
102.
[0175] Referring to FIG. 18, center section 101 is bored in a rear
portion thereof with a vertical fluid passage hole serving as
passage 34, and provided therein with upper and lower charge check
valves 35 interposed between fluid passage hole 34 and respective
upper and lower parallel fluid passage holes 21 and 27d. Each of
charge check valves 35 allows only flow from fluid from fluid
passage hole (passage) 34 to corresponding fluid passage hole
(passage) 21 or 27d (i.e., prevents backflow to fluid passage hole
34). Fluid passage hole 34 is opened downward at the bottom surface
of center section 101, and connected an upwardly opened fluid
passage hole 99c of passage 99 bored in charge pump casing 102.
[0176] Referring to FIG. 18, charge pump casing 102 is fastened to
center section through bolts 150. Referring to FIGS. 20,24(a) and
24(b), charge pump casing 102 is provided at a bottom portion with
a downwardly opened vertical pin hole, which coaxially coincides
with an upwardly opened vertical pin hole bored in a bottom portion
of rear transaxle housing 1H. A lock pin 152 is fitted in the
coinciding pin holes of charge pump casing 102 and rear transaxle
housing 1H, so as to engage charge pump casing 102 to rear
transaxle 1H at a determined position.
[0177] Referring to FIG. 18, as mentioned above, upwardly opened
vertical fluid passage hole 22b and 27b are bored in charge pump
casing 102 so as to be coaxially connected to respective vertical
fluid passage holes 22c and 27c bored in center section 101.
Referring to FIGS. 18, 19, 20 and 24(a), front and rear laterally
horizontal joint plugs 22a and 27a are screwed into charge pump
casing 102 so as to be connected to respective fluid passage holes
22b and 27b. Right end portions of joint plugs 22a and 27a project
rightwardly outward from the right side surface of charge pump
casing 102, and from the right side surface of rear transaxle
housing 1H, so as to be provided with respective rightwardly
outward opened ports 1 a and 1b. In this way, passage 22 between
hydraulic pump P (pump kidney port 57b) and port 1a in rear
transaxle housing 1H is constituted by the series of fluid passage
holes 22d, 22c, 22b and joint plug 22a, while passage 27 between
hydraulic motor M1 (motor kidney port 56b) and port 1b in rear
transaxle housing 1H is constituted by the series of fluid passage
holes 27e, 27d, 27, 27b and joint plug 27a. Incidentally, front
joint plug 22a with port 1a is higher than rear joint plug 27a with
port 1b. In this regard, vertical fluid passage hole 27b is bored
deeper than vertical fluid passage hole 22b.
[0178] Referring to FIG. 24(a), charge pump casing 102 is bored
with a vertical circular cylindrical trochoid gear chamber 137
which is opened upward to face the bottom surface of center section
101. Referring-to FIGS. 21 and 24(a), a circular (in plan view)
shaft hole 137a, into which the lower portion of input shaft 17 is
rotatably inserted, is extended downward from a bottom center
portion of trochoid gear chamber 137. Charge pump casing 102 is
bored from the bottom surface of trochoid gear chamber 137 with a
vertical suction port 58a on the left side of shaft hole 137a, and
with a vertical delivery port 58b on the right side of shaft hole
137a. Referring to FIG. 21, a trochoid gear consisting of an inner
gear 135 and an outer gear 136 is disposed in gear chamber 137.
Inner gear 135 is fixed on input shaft 17 inserted in shaft hole
137a, so as to be rotatable integrally with input shaft 17.
[0179] Referring to FIGS. 23 and 24(a), a fore-and-aft horizontal
fluid passage hole serving as suction passage 31 is bored in charge
pump casing 102, connected at a rear end thereof to suction port
58a, and forwardly outward opened at a recess 32d formed on the
front side surface of charge pump casing 102. Horizontal fluid
filter 32 is fitted at a rear end thereof into recess 32d so as to
be fluidly connected to suction passage hole 31.
[0180] Referring to FIGS. 21 and 24(a), a lateral horizontal fluid
passage hole 98b serving as a part of passage 98 is bored in charge
pump casing 102, connected at a left end thereof to delivery port
58b, and connected at a right end thereof to a lateral horizontal
joint plug 98a screwed into charge pump casing 102. A right end
portion of joint plug 98a projects rightwardly outward from the
right side surface of charge pump casing 102, and from the right
side surface of rear transaxle housing 1H, so as to be provided
with rightwardly outward opened port 75. In this way, passage 98
interposed between the delivery port of charge pump 33 and port 75
is constituted by fluid passage hole 98b and joint plug 98a.
[0181] Referring to FIGS. 24(a) and 24(b), a downwardly opened
groove of charge pump casing 101 and an upwardly opened groove of
charge pump 102 along a right side edge of trochoid gear chamber
137 coincide with each other so as to form a substantially
fore-and-aft fluid passage hole 99c. Referring to FIGS. 22 and
24(a), a lateral horizontal fluid passage hole 99b is bored in
charge pump casing 102 leftwardly upward from fluid passage hole
98b, connected at a left end portion thereof to an intermediate
portion of fluid passage hole 99c, and connected at a right end
portion thereof to a joint plug 99a screwed into charge pump casing
102. A right end portion of joint plug 99a projects rightwardly
outward from the right side surface of charge pump casing 102, and
from the right side surface of rear transaxle housing 1H, so as to
be provided with rightwardly outward opened port 76.
[0182] Referring to FIGS. 18 and 24(b), the bottom opening of
vertical fluid passage hole 34 is connected to a rear end portion
of fluid passage hole 99c. As mentioned above, in center section
101, fluid passage hole 34 is connected to fluid passage holes 21
and 27d through respective charge check valves 35. In this way,
joint plug 99a and fluid passage holes 99b and 99c constitute
passage 99 interposed between port 76 and either lower pressurized
passage 21 or 27 connected to the suction side of hydraulic pump P
through corresponding charge check valve 35.
[0183] Referring to FIGS. 18 and 24(a), check valve 39 is disposed
at a front end portion of fluid passage hole 99c. A fluid passage
hole 50a is extended from an intermediate portion of fluid passage
hole 99c to relief valve 50. Referring to FIGS. 22 and 24(a), a
fluid passage hole 36b from a relief valve 36 is connected to a
bottom portion of fluid passage hole 99c joining fluid passage hole
99b. Check valve 39, relief valve 50 and relief valve 36 will be
detailed later.
[0184] The above arrangement of rear transaxle 1 shown in FIGS. 16
to 24 is associated with the arrangement of vehicle 100 shown in
FIG. 3 or 9, so that ports 1a, 1b, 75 and 76 are provided on the
respective right outer ends of joint plugs 22a, 27a, 98a and 99a
projecting rightwardly outward from charge pump casing 102 through
the right side wall of rear transaxle housing 1H. Therefore, pipes
23, 26, 81 and 82 can be compactly collected to be connected to
respective ports 1a, 1b, 75 and 76. Alternatively, for the
arrangement of vehicle 100 shown in FIG. 5, rear transaxle 1 may be
disposed so that ports 1a, 1b, 75 and 76 are provided on the
respective left outer ends of joint plugs 22a, 27a, 98a and 99a
projecting leftwardly outward from charge pump casing 102 through
the left side wall of rear transaxle housing 1H.
[0185] As shown in FIG. 16, front axle-driving hydraulic fluid port
1a is disposed higher than rear axle-driving hydraulic fluid port
1b, and front auxiliary (power steering) device driving hydraulic
fluid port 75 is disposed lower than rear auxiliary (power
steering) device driving hydraulic fluid port 76. Due to the height
difference, ports 1a, 1b, 75 and 76 are disposed compactly in the
fore-and-aft direction, and pipes 23, 27, 81 and 82 connected these
ports can be smoothly extended forwardly upward without stressing
bend, thereby being further compactly collected.
[0186] A mechanism for controlling the tilt angle and direction of
movable swash plate Pa of hydraulic pump P will be described.
Referring to FIG. 21, a horizontal control shaft 113 rotatably
penetrates a right side wall of rear transaxle housing 1H. A
control arm 114 is fixed on an inner end of control shaft 113
inside housing 1H and engages at a top portion thereof with swash
plate Pa. Speed control lever 14 operatively connected to speed
control pedal 13 is fixed on control arm 114 outside housing
1H.
[0187] Referring to FIGS. 21 and 23, a torque spring 115 is wound
around control shaft 113 inside housing 1H and includes twisted and
extended opposite end portions, so as to pinch a pin (not shown)
fixed on control arm 114 and a retaining pin 117 planted into the
right side wall of housing 1H. Referring to FIGS. 16 and 21,
retaining pin 117 projects outward from housing 1H so as to be
provided thereon with a nut 116 for fastening retaining pin 117 to
housing 1H. Unless speed control pedal 13 is depressed, the force
of spring 115 pinching both retaining pin 117 and the pin fixed on
arm 114 keeps swash plate Ma at the neutral position. When speed
control pedal 13 is depressed on either front or rear side thereof,
swash plate Pa is tilted integrally with the rotation of lever 14,
shaft 113 and arm 114 so that spring 115 pushes the pin fixed on
arm 114 at one end thereof away from retaining pin 117 retaining
the other end thereof, so as to generate the neutral-returning
biasing force. Due to the neutral-returning biasing force of spring
115, swash plate Pa is kept at the tilt position corresponding to
the depression angle and direction of speed control pedal 13, and,
if speed control pedal 13 is released from depression force, swash
plate Pa and speed control pedal 13 return to the respective
neutral positions.
[0188] The flow of fluid in HST circuit HC1, especially in rear
transaxle 1, during forward traveling will be described. By
depressing speed control pedal 13 in the direction for forward
traveling, swash plate Pa of hydraulic pump P is tilted from the
neutral position (where swash plate Pa is disposed perpendicular to
input shaft 17, as shown in FIG. 23) to a position corresponding to
the depression degree and direction of speed control pedal 13. In
this state, cylinder block 104 is rotated integrally with input
shaft 17 so as to reciprocate pitons 109 at a stroke corresponding
to the tilt angle of movable swash plate Pa, whereby hydraulic pump
P sucks fluid from right pump kidney port 57a into the cylinder
holes of cylinder block 104, and delivers fluid from the cylinder
holes to left pump kidney port 57b.
[0189] Referring to FIGS. 2, 3, 18 and 20, fluid in pump kidney
port 57b from hydraulic pump P is led to port 1b through passage 27
consisting of fluid passage holes 27e, 27d, 27c and 27b and joint
plug 27a. In this state, corresponding charge check valve 35
prevents high-pressurized fluid in passage 27 from entering charge
fluid passage 34. Fluid flows from port 1b of rear transaxle 1 to
hydraulic motors M2 and M3 in front transaxle 2 through pipe 26,
and returns to port 1a of rear transaxle 1 through pipe 23.
Referring to FIGS. 18 and 19, in rear transaxle 1, fluid is
introduced into front motor kidney port 56b through passage 22
consisting of joint plug 22a and fluid passage holes 22b, 22c and
22d. Referring to FIG. 17, fluid is introduced from front motor
kidney port 56b into the cylinder holes of cylinder block 120 of
hydraulic motor M1 so as to reciprocate pitons 123 at a stroke
corresponding to the tilt angle of fixed swash plate Ma, thereby
rotating cylinder block 120 with motor shaft 127 for forward
traveling rotation. Referring to FIGS. 17, 18 and 20, the fluid in
the cylinder holes of cylinder block 120 is delivered into rear
motor kidney port 56a, and returns through passage 21 to right pump
kidney port 57a serving as the suction port of hydraulic pump P. In
this state, corresponding charge check valve 35 prevents
high-pressurized fluid in passage 21 from entering charge fluid
passage 34.
[0190] When speed control pedal 13 is depressed in the direction
for backward traveling, the above fluid flow route is reversed.
That is, left pump kidney port 57b serves as the suction port of
hydraulic pump P, and right pump kidney port 57a serves as the
delivery port of hydraulic pump P, so as to rotate motor shaft 127
for backward traveling rotation.
[0191] The fluid flow concerned to charge pump 33 will be described
with reference to FIGS. 2,21 and 23. The trochoid gear consisting
of inner and outer gears 135 and 136, serving as charge pump 33, is
driven by input shaft 17 so as to suck fluid from the fluid sump in
rear transaxle housing 1H into trochoid gear chamber 137 through
fluid filter 32, suction passage hole 31 and suction port 58a.
Charge pump 33 pressurizes fluid in trochoid gear chamber 137 and
delivers it to deliver port 58b. Relief valve 50 regulates the
pressure of delivery fluid from deliver port 58b so as to
correspond to the power steering device. The pressure-regulated
fluid from relief valve 50 is led into port 75 through passage 98
consisting of fluid passage hole 98b and joint plug 98a, and
supplied from port 75 to power steering hydraulic valve 80 through
pipe 81. Fluid drained from valve 80 returns to port 76 of rear
transaxle 1 through pipe 82. Fluid is supplied from valve 80 to one
chamber of power steering cylinder 79 through either pipe 83 or 84,
and simultaneously drained to the other chamber of power steering
cylinder 79 through the other pipe 84 or 83, thereby telescoping
piston rod 90 of cylinder 79.
[0192] Referring to FIGS. 18, 20 and 24(b), fluid returned from
valve 80 to port 76 is introduced to charge fluid passage 34
through passage 99 consisting of joint plug 99a and fluid passage
holes 99b and 99c, and supplied to either lower-pressurized passage
21 and pump kidney port 57a, during forward traveling, or
lower-pressurized passage 27 and pump kidney port 57b, during
backward traveling, through corresponding charge check valve
35.
[0193] The power transmission mechanism in rear transaxle 1 between
motor shaft 127 and axles 6 will be detailed with reference to FIG.
17. Deceleration gear train 37 comprises a diametrically large gear
37a, a diametrically small gear 37b, a counter shaft 37c and a
sleeve 37d. In the transmission gear chamber of rear transaxle
housing 1H, laterally horizontal counter shaft 37c is fixedly
spanned between the left side wall of housing 1H and the partition
wall in housing 1H behind motor shaft 127 and in front of axles 6.
Sleeve 37d is relatively rotatably provided on counter shaft 37c,
and diametrically large and small gears 37a and 37b are fixed on
sleeve 37d. Large gear 37a meshes with gear 127b fixed on motor
shaft 127, and small gear 37b meshes with a bull gear 38a of
differential gear unit 38.
[0194] Differential gear unit 38 comprises bull gear 38a, a pair of
left and right differential side gears 38b, and pinions 38c.
Differential side gears 38b are not-relatively rotatably
(spline-fittingly) provided on respective proximal end portions of
left and right axles 6. Pinions 3 8c are relatively rotatably
supported in bull gear 37a, so as to have pivots disposed in the
radial direction of bull gear 37a. Each pinion 38c meshes with both
differential side gears 38b, so as to differentially distribute the
rotary force of bull gear 37a between left and right axles 6.
[0195] Referring to FIG. 19, a vertical brake camshaft 143 is
rotatably supported in rear transaxle housing 1H. A brake arm 142
is fixed on a top portion of brake camshaft 143 projecting upward
from rear transaxle housing 1H, and operatively connected to brake
pedal 41 through a linkage. In rear transaxle housing 1H, brake
camshaft 142 is formed at a vertically intermediate portion thereof
with a sectionally semicircularly shaped cam 144 facing brake disc
140 on motor shaft 127 through a brake shoe 141. When brake pedal
41 is depressed, brake arm 142 and brake camshaft 143 are
integrally rotated, so as to slant cam 144 when viewed in plan, and
press brake shoe 141 against brake disc 140, thereby braking motor
shaft 127.
[0196] A safety valve device for the hydraulic circuit system will
be described with reference to FIGS. 18, 20 and 24(a). As mentioned
above, check valve 39 is disposed at the front end of fluid passage
hole 99c in charge pump casing 102. In charge pump casing 102, a
vertical fluid passage hole 39a is extended downward from check
valve 39, and a leftwardly horizontal fluid passage hole 39b is
extended leftward from a bottom portion of vertical fluid passage
hole 39a, so as to be connected to suction passage hole 31.
[0197] When vehicle 100 is parked on a slope, hydraulic motor M1
receives backflow driving force from wheels 7 and acts as a pump so
as to excessively pressurize HST circuit HCR. Hydraulic pump P and
charge pump 33 are not driven, and movable swash plate Pa of pump P
is disposed at the neutral position. However, due to the excessive
pressurization by hydraulic motor M1, fluid leaks from the gap
between hydraulic pump P and pump contact surface 103 or the gap
between hydraulic motor M1 and motor contact surface 129.
Consequently, HST circuit HC1 becomes short of fluid so as to cause
unexpected free rotation of hydraulic motor M1, i.e., cause the
free wheel phenomenon that vehicle 100 unexpectedly descends the
slope. Therefore, when HST circuit HC1 is hydraulically depressed
by the fluid leak, check valve 39 is automatically opened to pass
fluid from the fluid sump in rear transaxle housing 1H to either or
both of passage 21 and 27 through check valve or valves 35. In this
way, even while charge pump 33 is inactivated, check valve 39
supplies HST circuit HCl with fluid so as to prevent the free wheel
phenomenon.
[0198] Referring to FIGS. 22 and 23, charge pump casing 102 is
bored in a left rear portion thereof with a lateral horizontal
circular hole, into which pressure-regulating relief valve 36 is
fitted. A horizontal fluid passage hole 36a is extended rightward
from the upstream side of relief valve 36, and a vertical fluid
passage hole 36b is extended upward from fluid passage hole 36a to
fluid passage hole 99c, so as to connect the upstream side of
relief valve 36 to lower-pressurized passage 99 (fluid passage hole
99c). A vertical fluid passage hole 36c is extended downward from
the downstream side of charge pump 36 and downwardly outwardly
opened at the bottom surface of charge pump casing 102 to the fluid
sump in rear transaxle housing 1H. When the charge fluid circuit is
excessively supplied with fluid and the pressure in passage 99
excesses a predetermined level, relief valve 36 is opened to drain
fluid from passage 99 to the fluid sump outside of charge pump
casing 102 through fluid passage holes 36b, 36a and 36c, thereby
keeping the proper pressure level of fluid charged to the
axle-driving hydraulic fluid circuit in HST circuit HC1.
[0199] Referring to FIGS. 18 and 20, charge pump casing 102 is
bored in a rear bottom portion thereof with a fore-and-aft
horizontal circular hole, into which pressure-regulating relief
valve 50 for regulating pressure in the auxiliary (e.g., power
steering) device driving fluid circuit is fitted. The upstream side
of relief valve 50 is connected to higher-pressurized fluid passage
hole 98b, and the downstream side of relief valve 50 is connected
to lower-pressurized fluid passage hole 99c through a vertical
fluid passage hole 50a. In the auxiliary device driving fluid
circuit, if higher-pressurized passage 98 is excessively
pressurized, relief valve 50 is opened to bypass fluid from
higher-pressurized passage 98 to lower-pressurized passage 99.
[0200] Referring to FIG. 19, rear transaxle 1 is provided with a
forcible relief valve 160 comprising a lever 161, a camshaft 162,
and a pushpin 163. Vertical camshaft 163 is rotatably fitted at a
cam-shaped bottom portion into center section 101. Horizontal
pushpin 163 is axially slidably disposed in center section 101
between motor contact surface 129 and the cam portion of camshaft
163. Horizontal lever 161 is fixed on a top portion of camshaft 162
projecting upward from rear transaxle housing 1H. When vehicle 100
is towed, wheels 7 and 9 are requested to rotate freely from the
hydraulic pressure in HST circuit HC1. Therefore, lever 161 is
manually rotated together with camshaft 162 so that the cam portion
of camshaft 162 thrusts pushpin 163 outward from motor contact
surface 129, thereby pushing and separating cylinder block 120 from
motor contact surface 129, and draining fluid from motor kidney
ports 56a and 56b to the fluid sump in rear transaxle housing 1H.
In this way, fluid in HST circuit HC1 is reduced so as to allow the
free rotation of wheels 7 and 9.
[0201] Rear transaxle 1 is provided with a mechanism for expanding
the neutral dead zone of hydraulic pump P relative to the tilt of
movable swash plate Pa. Referring to FIG. 21, in center section
101, upper and lower horizontal fluid passage holes 171 and 172 are
extended rightward from respective upper and lower fluid passage
holes 21 and 27d, and opened rightwardly outward at the right side
surface of center section 101. A pair of upper and lower plugs
provided at right end portions with respective rightwardly outward
opened orifices 171a and 172a are fitted leftward into upper and
lower fluid passage holes 171 and 172, and project at the right end
portions thereof from the right openings of fluid passage holes 171
and 172 on the right side surface of center section 101. A portion
of control arm 114 opposite to the end engaged to swash plate Pa
with respect to control shaft 113 is extended so as to abut against
the right end of the plugs. A groove 114a constantly opened to the
fluid sump in rear transaxle housing 1H is formed on the surface of
the extended portion of control arm 114 facing the plugs so as to
correspond to a tilt range of swash plate Pa for making the
expanded neutral dead zone of hydraulic pump P.
[0202] While swash plate Pa is disposed within the tilt range
including the neutral position so that either or both of orifices
171a and 172a are opened to groove 114a (in FIG. 21, both orifices
171a and 172a are opened to groove 114a), a certain amount of fluid
is drained from higher-pressurized passage 21 or 27 to the fluid
sump through orifice 171a or 172a and groove 114a, so as to prevent
hydraulic pump P from supplying fluid to hydraulic motors M1, M2
and M3, thereby ensuring the extended neutral dead zone of
hydraulic pump P for preventing vehicle 100 from moving. The tilt
angle of movable swash plate Pa with control arm 114 from the
neutral position is increased so as to take groove 114a apart from
both orifices 171a and 172a, both the right end openings of
orifices 171a and 172a are closed by the surface of the extended
portion of control arm 114 so as to prevent fluid from being
drained from higher-pressurized passage 21 or 27, thereby ensuring
the proper volumetric efficiency between hydraulic pump P and
hydraulic motors M1, M2 and M3.
[0203] Alternatively, to expand the tilt range for the neutral dead
zone of hydraulic pump P, a check and neutral valve may be
interposed between passages 21 and 27.
[0204] Alternatively, referring to FIG. 25, a pump housing PH
incorporating hydraulic pump P and charge pump 33 is disposed
outside of rear transaxle housing 1H which incorporates hydraulic
motor M1, deceleration gear train 37, differential gear unit 38 and
axles 6.
[0205] Referring to FIG. 25, port 1a connected to external pipe 23
is disposed on rear transaxle housing 1H, and hydraulic motor M1 is
connected to port 1a through passage 22 in rear transaxle housing
1H. Port 1b connected to external pipe 26 is disposed on an outer
surface of pump housing PH, and hydraulic pump P is connected to
port 1b through passage 27 in pump housing PH. An outward opened
port 77a is disposed on an outer surface of pump housing PH, and a
port 77c is disposed on an outer surface of rear transaxle housing
1H. Passage 21 is disposed in pump housing PH, and interposed
between hydraulic pump P and port 77a. A passage 77d is disposed in
rear transaxle housing 1H, and interposed between hydraulic motor
M1 and port 77c. An external pipe 77b is disposed outside of pump
housing PH and rear transaxle housing 1H, and interposed between
ports 77a and 77c. Ports 75 and 76 connected to respective external
pipes 81 and 82 are disposed on the same outer side surface of pump
housing PH with port 1a. In pump housing PH are disposed the charge
fluid circuit portion between fluid filter 32 and port 75 through
charge pump 33 and passage 98, the charge fluid circuit portion
between port 76 and passages 21 and 27 through passage 99 and
charge check valves 35, and associate valves and equipments, which
are disposed in rear transaxle housing 1H in the embodiment of FIG.
2.
[0206] Pump housing PH is disposed adjacent to rear transaxle
housing 1H (e.g., just in front of housing 1H or just above housing
1H). Preferably, ports 1b, 75 and 76 are disposed on a right side
surface of pump housing PH while port 1a is disposed on the right
side surface of rear transaxle housing 1H, thereby collecting ports
1a, 1b, 75 and 76 at the right side of vehicle 100 so as to
compactly collect pipes 23, 26, 81 and 82. Alternatively, if port
1a is disposed on the left side surface of rear transaxle housing
1H, ports 1b, 75 and 76 are disposed on the left side surface of
pump housing PH.
[0207] Alternative arrangements of joint plugs 22a and 27a having
respective ports 1a and 1b fitted into rear transaxle housing 1H
will be described with reference to FIGS. 33(a) and 33(b) (each of
FIGS. 33(a) and 33(b) illustrates only representative joint plug
22a). Joint plugs 22a and 27a are provided thereon with respective
O-rings 175 in respective plug holes through the wall of rear
transaxle housing 1H. Further, referring to FIGS. 33(a), each of
the plug holes within the wall of rear transaxle housing 1H is
tapped, and each of joint plugs 22a and 27a has an intermediate
threaded portion corresponding to the tapped plug hole, so as to be
immovably fastened to rear axle housing 1H, while each of joint
plugs 22a and 27a are slidably fitted into charge pump casing 102.
Due to the screw-engagement of joint plugs 22a and 27a to rear
transaxle housing 1H, joint plugs 22a and 27a are prevented from
being axially deviated by movement of pipes 23 and 26 according to
the swing of front transaxle 2 around center pivot 5, thereby
preventing fluid leak from the gap between O-ring 175 and the
peripheral wall surface of the shaft hole in rear transaxle housing
1H. Referring to FIG. 33(b), for the same purpose of the
arrangement of FIG. 33(a), a flange 176 is fixed on the outer
peripheral portion of each of joint plugs 22a and 27a projecting
outward from rear axle housing 1H, and flange 176 is fastened onto
the outer side surface of rear transaxle housing 1H through bolts
or screws. In this way, the arrangements shown in FIGS. 33(a) and
33(b) improve the fluid tightness of joint plugs 22a and 27a
against rear transaxle housing 1H.
[0208] Alternatively, vehicle 100 may be provided at a front
portion thereof with transaxle 1 incorporating hydraulic motor M1,
deceleration gear train 37 and differential gear unit 38, and
provided at a rear portion thereof with transaxle 2 incorporating
hydraulic motors M2 and M3. In this regard, front wheels may be
unsteerable, and rear wheel may be steerable.
Second Embodiment
[0209] Each of hereinafter described vehicles 200 and 300 is
provided with front transaxle 2 in which positions or directions of
ports 2a and 2b are different from those of front transaxle 2 of
vehicle 100. Referring to FIG. 10, vehicle 200 according to a
second embodiment is provided with front transaxle 2 serving as
laterally reversed front transaxle 2 of vehicle 100. Namely, in
front transaxle 2 of this embodiment, right fixed displacement
hydraulic motor M2 and left variable displacement hydraulic motor
M3 are disposed in front transaxle housing 2H. In this regard, cam
mechanism CM for controlling the tilt of swash plate M3a of
hydraulic motor M3 is disposed leftward in front transaxle 2. Ports
2a and 2b are disposed on a laterally intermediate rear potion of
rear transaxle housing 2H so as to be rightwardly outward opened.
Further, referring to FIG. 10, ports 1a and 1b are disposed on the
right side surface of rear transaxle housing 1H. Vehicle 200
employs HST circuit HCl similar to that of FIG. 2.
[0210] To corresponding to rightward ports 2a and 2b on front
transaxle 2, pipes 23 and 26 interposed between respective rear
ports 1a and 1b and respective front ports 2a and 2b include
fore-and-aft main portions extended along right side plate 3R of
frame 3 (along the bottom edge of right side plate 3R when viewed
in side, and along the inside surface of right side plate 3R when
viewed in plan). Pipe 23 includes rear rigid pipe 23b connected to
port 1a, front rigid pipe 23c connected to port 2a, and flexible
hose 23a interposed between rear and front rigid pipes 23b and 23c.
Pipe 26 includes rear rigid pipe 26b connected to port 1b, front
rigid pipe 26c connected to port 2b, and flexible hose 26a
interposed between rear and front rigid pipes 26b and 26c. Rear
rigid pipes 23b and 26b are extended rightward from respective
ports 1a and 1b, bent and extended forwardly upward, and bent
against and extended horizontally forward, so as to be clamped by
clamping stay 62 fixed on the inside surface of right side plate
3R. Front rigid pipes 23c and 26c are extended in the fore-and-aft
direction along right side plate 3R of frame 3 (along the bottom
edge of right side plate 3R when viewed in side, and along the
inside surface of right side plate 3R when viewed in plan), and
connected to respective rear rigid pipes 23b and 26b through
respective swivel joints 54, and to respective front rigid pipes
23c and 26c through respective swivel joints 55. This arrangement
of pipes 23 and 26 serves as the laterally reversed arrangement of
pipes 23 and 26 shown in FIG. 5 where ports 1a and 1b are disposed
on the left side surface of rear transaxle housing 1H and ports 2a
and 2b are disposed on the left side surface of front transaxle
housing 2H. Further, tension pulley 52 with spring 53 also serves
as the laterally reversed tension pulley 52 shown in FIG. 3 so as
to be prevented from interfering with pipes 23 and 26 along right
side plate 3R.
[0211] This arrangement of pipes 23 and 26 between rear and front
transaxles 1 and 2 has the same advantages as the arrangement of
pipes 23 and 26 shown in the embodiment of FIG. 3 combined with the
embodiment of FIG. 5. That is, pipes 23 and 26 can be compactly
disposed at the safe space inside frame 3 while they are prevented
from interfering with the traveling power transmission system, the
mower-driving power transmission system and mower unit 20, from
having fluid leak and being damaged at ends thereof connected to
ports 1a, 1b, 2a and 2b, and from being subjected to twisting
stress caused by the swing of front transaxle 2 around center pivot
5. Further, since all rear ports 1a and 1b and front ports 2a and
2b are disposed rightward, rear rigid pipes 23b and 26b have no
laterally extended portions disposed just in front of rear
transaxle housing 1H, i.e., have bent portions reduced.
[0212] Referring to FIG. 10, power steering valve 80 (not shown) is
disposed on frame 3 between rear and front transaxles 1 and 2,
power steering cylinder 79 is attached onto the outside surface of
right side plate 3R, and ports 75 and 76 are disposed on the right
side surface of rear transaxle housing 1H. Therefore, pipes 81 and
82 are disposed along pipes 23 and 26 along right side plate 3R.
The arrangement of pipes 81, 82, 83 and 84 for power steering
serves as the laterally reversed arrangement of those shown in FIG.
5. Further, in association with the position of power steering
cylinder 79 rightward of frame 3, bracket 48a pivotally connected
to piston rod 90 of cylinder 79 is provided on right front wheel
support unit 48R in association with cam mechanism CM disposed
leftward on front transaxle 2. Other structure and parts in vehicle
200 are similar to vehicle 100 whose rear portion is configured as
shown in FIG. 5.
[0213] Referring to FIG. 11, in vehicle, pipes 23 and 26 interposed
between rightward opened ports 1a and 1b of rear transaxle 1 and
rightward opened ports 2a and 2b of front transaxle 2 comprise
flexible pipes 23d and 26d connected to ports 2a and 2b and rigid
pipes 23e and 26e connected to ports 1a and 1b. Rigid pipes 23e and
26e are extended along right side plate 3R, clamped by clamping
stays 62 and 63 fixed to right side plate 3R, and connected at
front ends thereof to respective rigid pipes 23d and 26d through
respective swivel joints 55. This arrangement of pipes 23 and 26
serves as the laterally reversed arrangement of pipes 23 and 26
shown in FIG. 9, excluding that flexible hoses 23e and 26e do not
have laterally extended portions disposed just in front of rear
transaxle housing 1H because ports 1a and 1b are disposed on the
right side surface of rear transaxle housing 1H. The increase of
rigid pipe portions in pipes 23 and 26 advantageously reduces
internal pressure resistance in pipes 23 and 26.
Third Embodiment
[0214] Referring to FIGS. 12 and 13, each of vehicles 300 according
to a third embodiment is provided with front transaxle 2
substantially similar to front transaxle 2 of vehicle 100 shown in
FIG. 3. That is, front transaxle housing 2H incorporates left fixed
displacement hydraulic motor M2 and right variable displacement
hydraulic motor M3, cam mechanism CM is disposed in the rightward
portion of front transaxle 2, and port 2a connected to pipe 23 is
rightwardly outward opened. The different point of rear transaxle 2
of vehicle 300 from that of vehicle 100 is that port 2b connected
to pipe 26 is rightwardly outward opened opposite to port 2a.
Further, referring to FIGS. 12 and 13, ports 1 a and 1b are
disposed on the right side surface of rear transaxle housing
1H.
[0215] Referring to FIGS. 12 and 13, to correspond to this
arrangement of ports la, 1b, 2a and 2b, arrangement of pipe 23
interposed between ports 1a and 2a is similar to that of vehicle
100 shown in FIG. 3, and arrangement of pipe 26 interposed between
ports 1b and 2b is similar to that of vehicle 200 shown in FIG. 10.
That is, pipe 23 includes the fore-and-aft main portion extended
along left side plate 3L (along the bottom edge of left side plate
3L when viewed in side and along the inside surface of left side
plate 3L when viewed in plan), and pipe 26 includes the
fore-and-aft main portion extended along right side plate 3R (along
the bottom edge of right side plate 3R when viewed in side and
along the inside surface of right side plate 3R when viewed in
plan). In association with the laterally opposite arrangement of
ports 1a and 2a, pipe 23 includes the lateral extended portion
disposed just in front of rear transaxle housing 1H (and clamped by
clamping stay 60 fixed on rear transaxle housing 1H) so as to be
extended at the fore-and-aft main portion thereof along left side
plate 3L. On the other hand, since both ports 1b and 2b are opened
rightward, pipe 26 is extended from port 1b to the fore-and-aft
main portion thereof without bending to have a lateral extended
portion just in front of rear transaxle housing 1H.
[0216] More specifically, referring to FIG. 12, pipe 23 comprises
rear and front rigid pipes 23b and 23c and flexible hose 23a
interposed between rigid pipes 23b and 23c, and pipe 26 comprises
rear and front rigid pipes 26b and 26c and flexible hose 26a
interposed between rigid pipes 26b and 26c. Flexible hose 23a is
extended in the fore-and-aft direction along left side plate 3L,
connected at the rear end thereof through swivel joint 54 to rear
rigid pipe 23b connected to port 1a, and connected at the front end
thereof through swivel joint 55 to front rigid pipe 23c connected
to port 2a. Flexible hose 26a is extended in the fore-and-aft
direction along right side plate 3R, connected at the rear end
thereof through swivel joint 54 to rear rigid pipe 26b connected to
port 1b, and connected at the front end thereof through swivel
joint 55 to front rigid pipe 26c connected to port 2b. Rear rigid
pipe 23b includes the lateral extended portion which is disposed
just in front of rear transaxle housing 1H and clamped by clamping
stay 60 fixed on rear transaxle housing 1H. The forwardly extended
front portion of rear rigid pipe 23b is clamped by clamping stay 61
fixed to left side plate 3L so as to be connected to flexible hole
23a through swivel joint 54. Rear rigid pipe 26b includes no
lateral extended portion disposed just in front of rear transaxle
housing 1H, but is extended substantially forward when viewed in
plan so as to be connected to flexible hose 26R through swivel
joint 54.
[0217] Referring to FIG. 13, pipe 23 comprises flexible hose 23d
connected to port 2a, and rigid pipe 23e connected to port 1a. Pipe
26 comprises flexible hose 26d connected to port 2b, and rigid pipe
26e connected to port 1b. Rigid pipe 23e includes the fore-and-aft
extended portion along left side plate 3L, and is connected at the
rear end thereof to port 1a, and at the front end thereof to
flexible hose 23d through swivel joint 55. Further, rigid pipe 23e
includes the lateral extended portion which is disposed just in
front of rear transaxle housing 1H and clamped by clamping stay 60
fixed on rear transaxle housing 1H. The front portion of rigid pipe
23e is clamped by clamping stay 61 fixed to left side plate 3L so
as to be connected to flexible hose 23d through swivel joint 55.
Rigid pipe 26e includes the fore-and-aft extended portion along
right side plate 3R, and is connected at the rear end thereof to
port 1b, and at the front end thereof to flexible hose 26d through
swivel joint 55. Rigid pipe 26e includes no lateral extended
portion disposed just in front of rear transaxle housing 1H, but is
extended substantially forward when viewed in plan so as to be
disposed along right side plate 3R, and connected at the front end
thereof to flexible hose 26d through swivel joint 55.
[0218] Other features and advantages in these arrangements of pipes
23 and 26 in FIGS. 12 and 13 are the same as those in the above
descriptions about the embodiments of FIGS. 3, 9, 10 and 11.
[0219] Further, referring to FIGS. 12 and 13, power steering device
80 is disposed between rear and front transaxles 1 and 2, and power
steering cylinder 79 is disposed along left side plate 3L and
includes piston rod 90 connected to bracket 48a mounted on left
front wheel support unit 48L. Ports 76 and 78 are disposed on the
same right side surface of rear transaxle housing 1H with ports 1a
and 1b. In this condition, pipes 81 and 82 interposed between valve
80 and respective ports 75 and 76, and pipes 83 and 84 interposed
between valve 80 and cylinder 79 are disposed similar to those in
the arrangement of FIG. 3. In this regard, pipes 81 and 82 are
disposed along pipe 26 along right side plate 3R. The features and
advantages of the arrangement of power steering pipes are the same
as those in the above description of FIG. 3.
[0220] Alternatively, each of vehicle 300 may be provided with any
of rear transaxles 1 arranged as shown in FIGS. 5, 6 and 7. If
either of rear transaxles 1 shown in FIGS. 5 and 7 is equipped on
vehicle 300, since ports 1a and 1b are disposed leftward of rear
transaxle housing 1H, pipe 26 including the fore-and-aft main
portion extended along right side plate 3R includes the lateral
extended portion disposed just in front of rear transaxle 1, and
pipe 23 including the fore-and-aft main portion extended along left
side plate 3L includes no lateral extended portion disposed just in
front of rear transaxle 1. Pipes 81 and 82 are disposed along pipe
23 along left side plate 3L.
Fourth Embodiment
[0221] Each of hereinafter described vehicles 400 and 500 is
provided with a reservoir tank arranged in a different manner from
that of reservoir tank 28 in vehicle 100. Referring to FIG. 14, in
vehicle 400 according to a fourth embodiment, a reservoir tank 428
is joined to a fuel tank FT. Fuel tank FT and reservoir tank 428
are disposed between rear transaxle 1 and driver's seat 16 above
rear transaxle 1, i.e., below driver's seat 16 and above rear
transaxle 1. A breather 442 of reservoir tank 428, also serving as
a fluid-supply opening of reservoir tank 428, is disposed behind
seat 16.
[0222] More specifically, in rear cover 15 on the rear portion of
frame 3 is disposed a tank 451 whose inner space is divided into
front and rear chambers by a partition 450. The front chamber in
tank 451 serves as fuel tank FT. The rear chamber serves as
reservoir tank 428, which is disposed just behind seat 16 mounted
on the top of rear cover 15 in the fore-and-aft direction of
vehicle 400.
[0223] The top portion of rear cover 15 is bored with a hole just
behind seat 16. An upright cylindrical fluid-supply portion 428a
projects upward from tank 428 through the hole of rear cover 15
just behind seat 16. Breather 442 is provided on the top of
fluid-supply portion 428a. Fluid-supply portion 428a is opened at
the bottom thereof to fluid tank 428 in tank 451. A fuel-supply
opening is disposed on the top of fuel tank FT of tank 451 under
seat 16. Reservoir tank 428 is disposed so that the fluid level in
reservoir tank 428 is higher than the fluid levels of the
respective fluid sumps in rear and front transaxles 1 and 2.
Reservoir tank 428 is fluidly connected to the fluid sump of rear
transaxle 1 through drain pipe 29, and to the fluid sump of front
transaxle 2 through drain pipe 30, so as to absorb excessive fluid
from the respective fluid sumps.
[0224] The integration of reservoir tank 428 with fuel tank FT is
advantageous in saving the number of required parts, and
facilitates assembly of the reservoir tank and the fuel tank. Due
to the position of reservoir tank 428 just above the rear end of
frame 3, the length of drain pipe 30 interposed between reservoir
tank 428 and front transaxle 2 is enough to ensure adequate
flexibility of drain pipe 30 following the swing of front transaxle
2 around center pivot 5.
[0225] Further, referring to FIG. 14, vehicle 400 is provided with
left and right mower hangers 491 whose respective pivots 92 are
disposed coaxially to axles 8 supported by rear transaxle housing
2H. Mower hangers 491 are pivoted at top portions thereof on
respective pivots 92, and extended downward. Left and right link
rods 91a are pivoted at front ends thereof onto bottom portions of
mower hangers 491, and hooked at rear ends thereof onto the front
end of mower unit 20. Since pivots 92 of mower hangers 491 are
disposed coaxially to axles 8, the accuracy of location of mower
hangers 491 is improved so as to facilitate assembly work of
suspending mower unit 20.
Fifth Embodiment
[0226] Referring to FIG. 15, in vehicle 500 of a fifth embodiment,
a reservoir tank 528 is disposed between rear wheels 7 and front
wheels 9, and in bonnet 11 incorporating engine 10. A breather 542
of reservoir tank 528, also serving as a fluid-supply opening of
reservoir tank 528, is disposed so as to face an opening 543
provided in the dashboard at the rear end of bonnet 11. Opening 543
is normally covered with a lid 543.
[0227] More specifically, in bonnet 11, reservoir tank 528 is
disposed upright just behind engine 10 between front wheels 9 and
rear wheels 7. The bottom of reservoir tank 528 is disposed at the
vertical intermediate position of the inside of bonnet 11. A
cylindrical upright fluid-supply portion 528a projects upward from
the top of reservoir tank 528. A breather 542, also serve as a
fluid-supply opening of reservoir tank 528, is disposed on the top
of fluid-supply portion 528a so as to face the opening of the
dashboard covered with lid 543. Reservoir tank 528 is fluidly
connected to the fluid sump of rear transaxle 1 through drain pipe
29, and to the fluid sump of front transaxle 2 through drain pipe
30, so as to absorb excessive fluid from the respective fluid
sumps.
[0228] Since reservoir tank 528 is disposed between rear wheels 7
and front wheels 9, reservoir tank 528 approaches the fore-and-aft
middle portion of vehicle 500 so as to ensure good balance of
vehicle 500 in the fore-and-aft direction. Due to the upright shape
of reservoir tank 528, the fluid in reservoir tank 528 is prevented
from being contaminated with air bubbles when vehicle 500 travels
on a slope. Further, reservoir tank 528 disposed just behind engine
10 is easily subjected to the air for cooling engine 10.
[0229] Further, vehicle 500 is provided with mower hangers 491
pivoted on pivots 92 disposed coaxially to axles 8, so as to
suspend mower unit 20 through link rods 91a , similar to those of
vehicle 400 in FIG. 14.
[0230] With respect to front transaxle 2, in each of the foregoing
embodiments of vehicles 100, 200, 300, 400 and 500, referring to
FIGS. 1 to 25, the arrangement of fixed displacement hydraulic
motor M2 and variable displacement hydraulic motor M3 for
respective axles 8 may be replaced with an arrangement of a single
(variable displacement) hydraulic motor and a differential gear
unit driven by the hydraulic motor. Left and right axles 8 mutually
connected through the differential gear unit can be differentially
driven similar left and right axles 8 driven by respective
hydraulic motors M2 and M3. The single variable displacement
hydraulic motor ensures acceleration of front wheels 9 during
turning of the vehicle. A pair of hydraulic pressure fluid
supply-and-delivery ports of the single hydraulic motor, and pipes
interposed between these ports and ports 1a and 1b on rear
transaxle 1 can be disposed on front transaxle housing 2H similar
to any of the foregoing arrangements of ports 2a and 2b and pipes
23 and 26.
Sixth Embodiment
[0231] Referring to FIGS. 16 to 32, a transaxle 601 may replace
rear transaxle 1 in the foregoing embodiments of vehicles 100 to
500 referring to FIGS. 1 to 24. Referring to FIG. 26, transaxle 601
includes housing 601H which is provided on a right side surface
thereof with ports 601a and 601 b for supply and delivery of
hydraulic pressure fluid for driving axles, and with ports 675 and
676 for supply and delivery of hydraulic pressure fluid for driving
an auxiliary (e.g., power steering) device. A hydraulic circuit of
a hydraulic four-wheel driving vehicle equipped with transaxle 601
can be similar to the hydraulic circuit shown in FIG. 2, on the
assumption that a hydraulic pump P6 and a hydraulic motor M6 in
transaxle 601 coincide to hydraulic pump P and hydraulic motor M1
in transaxle 1, and almost other concerned parts and devices of
transaxle 601 coinciding to those of transaxle 1 shown in FIG. 2
are marked by respective notations shown in FIG. 2 plus 600.
[0232] The main feature of transaxle 601 is that an adapter 693,
formed therein with a fluid passage hole to be interposed between
port 601a and a passage in a center section 691, is detachably
attached to center section 691, as shown in FIGS. 28 and 29, and a
joint plug 627a including port 601b is fitted into center section
691 to be connected to another passage in center section 691, as
shown in FIGS. 28 and 32(b).
[0233] A general structure and function of transaxle 601 will be
described. As shown in FIG. 27, the inner space of transaxle
housing 601H is partitioned by a partition wall between a hydraulic
circuit chamber and a transmission gear chamber. Hydraulic pump P6
and hydraulic motor M6 are disposed in the hydraulic circuit
chamber, and a deceleration gear train 637, a differential gear
unit 638 and axles 6 are disposed in the transmission gear chamber.
As shown in FIGS. 26 and 29, transaxle housing 601H is constituted
by upper and lower halves joined to each other through bolts
653.
[0234] Referring to FIG. 30, an upper portion of an input shaft 617
projects vertically upward from transaxle housing 601H, and is
fixedly provided thereon with input pulley 617a so as to be
drivingly connected to engine 10 through belt 18, and is fixedly
provided thereon with cooling fan 617b for cooling transaxle
housing 601H under pulley 617a. In transaxle housing 601H, vertical
input pulley 617 serves as the rotary axial shaft of hydraulic pump
P6.
[0235] Variable displacement hydraulic pump P6, having input shaft
617 serving as the vertical rotary axis thereof, is vertically
mounted onto a rear top surface of center section 691 at which
kidney ports 657a and 657b are opened. As shown in FIG. 27, fixed
displacement hydraulic motor M6, having a laterally (leftward)
horizontal motor shaft 727 serving as the rotary axis thereof, is
mounted onto a front left side surface of center section 691 at
which kidney ports 656a and 656b are opened, so as to be fluidly
connected to hydraulic pump P6. Motor shaft 727 is drivingly
connected to deceleration gear train 637 so as to transmit the
output force of hydraulic motor M6 to axles 6 through deceleration
gear train 637 and differential gear unit 638. 10234] As shown in
FIGS. 28 and 29, vertical input shaft 617 penetrates center section
691 and is inserted into a charge pump casing 692 attached to the
bottom surface of center section 691 so as to serve as the drive
shaft of charge pump 633 in charge pump casing 692. Charge pump 633
sucks fluid from the fluid sump in transaxle housing 601H so as to
supply fluid to the axle-driving hydraulic circuit, and to the
auxiliary device (power steering) driving hydraulic circuit through
ports 675 and 676.
[0236] As shown in FIGS. 26 and 30, speed control lever 614
operatively connected to speed control pedal 13 is pivoted on
transaxle housing 601H so as to control the tilt angle and
direction of a movable swash plate P6a of hydraulic pump P6.
[0237] The structure of the hydraulic circuit system in transaxle
601 will be more detailed. As shown in FIGS. 27 and 32(b), center
section 691 is fastened to an inside wall of transaxle housing 601H
through bolts 651. As shown in FIG. 27, the circular rear top
surface of center section 691, onto which hydraulic pump P6 is
mounted, serves as a pump contact surface 603. In pump contact
surface 603, a right pump kidney port 657a and a left pump kidney
port 657b are laterally symmetrically opened upward, and a vertical
shaft hole 617n, into which input shaft 617 is rotatably inserted,
is opened upward between right and left pump kidney ports 657a and
657b. Vertical shaft hole 617n is passed through center section 691
and also opened downward at the bottom surface of center section
691, as shown in FIG. 30.
[0238] As shown in FIGS. 27, 28 and 30, a cylinder block 604 of
hydraulic pump P6 is slidably rotatably fitted onto pump contact
surface 603 so as to open cylinder holes therein to kidney ports
657a and 657b, and is not-relatively rotatably fitted on input
shaft 617 passed through shaft hole 617n (in a spline-engaging
manner). Pistons 609 are reciprocally slidably fitted in the
respective cylinder holes of cylinder block 604, and project at
heads thereof outward from cylinder block 604 so as to abut against
movable swash plate P6a. Input shaft 617 projects upward from
cylinder block 604, freely penetrates movable swash plate P6a, and
projects upward from the top wall of rear transaxle housing 1H so
as to be fixedly provided thereon with pulley 617a and cooling fan
617b, as mentioned above. Input shaft 617 inserted in shaft hole
617n also projects downward from center section 691 into charge
pump casing 692 so as to serve as the drive shaft of charge pump
633.
[0239] Referring to FIGS. 27 and 28, a fore-and-aft horizontal
fluid passage hole 621 (coinciding to fluid passage hole 21 in
transaxle 1) interposed between hydraulic pump P6 and motor M6 is
bored in center section 101, so as to be connected at a rear upper
end portion to right pump kidney ports 657a, and at a front upper
end portion thereof to a rear motor kidney port 656a. In center
section 691 is bored therein with a part of a passage interposed
between hydraulic pump P6 and port 601b (coinciding to passage 27
of transaxle 1) comprising fluid passage holes 627b, 627d and 627e.
Fluid passage hole 627e is extended rightwardly downward from left
pump kidney port 657b to a fore-and-aft intermediate portion of
fluid passage hole 627d. Fluid passage hole 627d is fore-and-aft
horizontally extended under fluid passage hole 621 in parallel.
Fluid passage hole 627b is extended horizontally rightward from a
front end portion of fluid passage hole 627d, and opened outward at
a right side surface of center section 691. Joint plug 627a
provided at the outer end with port 601 b is inserted horizontally
leftward into fluid passage hole 627b through a right sidewall of
transaxle housing 601H, so as to be fluidly connected to left pump
kidney port 657b.
[0240] As shown in FIGS. 27 and 28, the circular front left side
surface of center section 291, onto which hydraulic motor M6 is
mounted, serves as a motor contact surface 729. In motor contact
surface 729, rear motor kidney port 756a and front motor kidney
port 756b are symmetrically opened leftward, and a lateral
horizontal shaft hole 727a, into which motor shaft 727 is rotatably
inserted, is opened leftward between rear and front motor kidney
ports 656a and 656b.
[0241] As shown in FIGS. 27 and 29, a cylinder block 720 of
hydraulic motor M6 is slidably rotatably fitted onto motor contact
surface 729 so as to open cylinder holes therein to kidney ports
656a and 656b, and is not-relatively rotatably fitted on motor
shaft 727 inserted in shaft hole 727a (in a spline-engaging
manner). Pistons 723 are reciprocally slidably fitted in the
respective cylinder holes of cylinder block 720, and project at
heads thereof outward from cylinder block 720 so as to abut against
a fixed swash plate M6a.
[0242] As shown in FIGS. 27 and 29, motor shaft 727, rotatably
fitted at a right end portion thereof in shaft hole 727a of center
section 691, is journalled through a bearing 728 by the partition
wall between the hydraulic circuit chamber and the transmission
gear chamber, and extended at a left end portion thereof into the
transmission gear chamber so as to be provided thereon with a gear
727b and a brake disc 740.
[0243] Referring to FIGS. 27 and 28, rear motor kidney port 656a is
connected to right pump kidney port 657a through horizontal fluid
passage hole (passage) 621, as mentioned above.
[0244] Referring to FIGS. 28, 29 and 32(b), a passage interposed
between hydraulic motor M6 and port 601a (coinciding to passage 22
of transaxle 1) is formed by adapter 693 attached to the bottom
surface of center section 691, horizontal joint plug 622a screwed
into adapter 693, and a vertical fluid passage plug 694 fitted into
center section 691 through adapter 693. In this regard, a vertical
hole 694b is bored vertically downward from front motor kidney port
656b and downwardly opened at the bottom surface of center section
691. Center section 691 and adapter 693 are bored with coaxial
vertical bolt holes 695b and 695a . Adapter 693 is fastened to this
bottom surface of center section 691 through a vertical bolt 695
screwed into bolt holes 695a and 695b . A vertical hole 694a is
bored through adapter 693 so as to be coaxially connected at the
top thereof to hole 694b in center section 691. Vertical fluid
passage plug 694 is upwardly inserted into hole 694b through hole
694a. A vertical axial fluid passage hole 622b is bored in plug
694. Hole 622b is opened at the top of plug 694 in hole 694b within
center section 691, and opened at a vertical intermediate portion
of plug through radial horizontal ports into hole 694a. A lateral
horizontal tapped hole is bored in adapter 693 so as to be
connected vertical hole 694a and opened rightwardly outward. Joint
plug 622a is screwed from the rightward outside of housing 601H
into the horizontal tapped hole in adapter 622a through the right
side wall of transaxle housing 601H. Joint plug 622a includes a
horizontal penetrating axial fluid passage hole whose outer right
end serves as port 601a . The fluid passage hole in joint plug 622a
is opened at the inward end into hole 694a so as to be fluidly
connected to vertical fluid passage hole 622b in plug 694, thereby
fluidly connecting port 601a to motor kidney port 656b opened to
hydraulic motor M6.
[0245] Alternatively, adapter 693 may be formed therein with a
fluid passage without fluid passage plug 694. Alternatively, both
fluid passages to respective ports 601a and 601b may be formed in
adapter 693. Alternatively, adapter 693 may be formed therein with
a fluid passage to port 601b, and a joint plug including port 601a
may be provided onto center section 691.
[0246] Joint plugs 622a and 627a are screwed into the tapped hole
in adapter 693 and tapped fluid passage hole 627b, respectively.
Alternatively, joint plugs 622a and 627a may be screwed in
respective tapped holes within the wall of transaxle housing 601H,
similar to joint plug 22a (27a) of FIG. 33(a), or they may be
fastened to the outer side surface of transaxle housing 601H
through a flange, thereby improving the fluid tightness thereof. In
either of the two cases, joint plugs 622a and 627a may be just
slidably fitted into the hole in adapter 693 and fluid passage hole
627b, respectively (without screwing engagement).
[0247] Referring to FIG. 28, center section 691 is bored in a rear
portion thereof with a vertical fluid passage hole 634, and
provided therein with upper and lower charge check valves 635
interposed between fluid passage hole 634 and respective upper and
lower parallel fluid passage holes 621 and 627d. Each of charge
check valves 635 allows only flow from fluid from fluid passage
hole 634 to corresponding fluid passage hole 21 or 27d (i.e.,
prevents backflow to fluid passage hole 634). Fluid passage hole
634 is opened downward at the bottom surface of center section 691,
and connected an upwardly opened fluid passage hole 699d bored in
charge pump casing 692.
[0248] Referring to FIGS. 28, 30, 31(a), 31(b), 32(a) and 32(b),
the structure charge pump 633 and charge pump casing 692 will be
described. As shown in FIGS. 32(a) and 32(b), charge pump casing
692 is fastened to center section through bolts 660. As shown in
FIG. 32(a), charge pump casing 692 is bored with a vertical
circular cylindrical trochoid gear chamber 737 which is opened
upward to face the bottom surface of center section 691. As shown
in FIGS. 30 and 32(a), circular (in plan view) shaft hole 737a,
into which the lower portion of input shaft 617 is rotatably
inserted, is extended downward from a bottom center portion of
trochoid gear chamber 737. Charge pump casing 692 is bored from the
bottom surface of trochoid gear chamber 737 with a vertical suction
port 658a on the left side of shaft hole 737a, and with a vertical
delivery port 658b on the right side of shaft hole 737a. As shown
in FIG. 30, a trochoid gear consisting of an inner gear 735 and an
outer gear 736 is disposed in gear chamber 737. Inner gear 735 is
fixed on input shaft 617 inserted in shaft hole 737a, so as to be
rotatable integrally with input shaft 617.
[0249] As shown in FIG. 32(a), a fore-and-aft horizontal fluid
suction passage hole 631 is bored in charge pump casing 692,
connected at a rear end thereof to suction port 658a, and forwardly
outward opened at a recess 632d formed on the front side surface of
charge pump casing 692. A horizontal fluid filter 632 is fitted at
a rear end thereof into recess 632d so as to be fluidly connected
to suction passage hole 631.
[0250] Referring to FIGS. 30 and 32(a), a lateral horizontal fluid
passage hole 698b is bored in charge pump casing 692, connected at
a left end thereof to delivery port 658b, and connected at a right
end thereof to a lateral horizontal joint plug 698a screwed into
charge pump casing 692. A right end portion of joint plug 698a
projects rightwardly outward from the right side surface of charge
pump casing 692, and from the right side surface of rear transaxle
housing 601H, so as to be provided with rightwardly outward opened
port 675. In this way, a passage (coinciding to passage 98 of
transaxle 1) interposed between the delivery port of charge pump
633 and port 675 is constituted by fluid passage hole 698b and
joint plug 698a.
[0251] Referring to FIGS. 32(a) and 32(b), a downwardly opened
groove of charge pump casing 691 and an upwardly opened groove of
charge pump 692 along a rear side edge of trochoid gear chamber 737
coincide with each other so as to form a substantially lateral
fluid passage hole 699d. Referring to FIGS. 31(a) and 32(a), a
vertical fluid passage hole 699c is extended downward from a right
end portion of fluid passage hole 699d, and connected at the bottom
thereof to a lateral horizontal fluid passage hole 699b. Fluid
passage hole 699b is opened rightwardly outward at the right side
surface of charge pump casing 692. A joint plug 699a is screwed
into fluid passage hole 699b. A right end portion of joint plug
699a projects rightwardly outward from the right side surface of
charge pump casing 692, and from the right side surface of
transaxle housing 601H, so as to be provided with rightwardly
outward opened port 676 adjacent to port 675.
[0252] Referring to FIGS. 28 and 32(b), the bottom opening of
vertical fluid passage hole 634 is connected to an intermediate
portion of fluid passage hole 699d. As mentioned above, in center
section 691, fluid passage hole 634 is connected to fluid passage
holes 621 and 627d through respective charge check valves 635. In
this way, joint plug 699a and fluid passage holes 699b and 699c
constitute a passage (coinciding to passage 99 of transaxle 1)
interposed between port 676 and either lower pressurized passage
hole 621 or 627d connected to the suction side of hydraulic pump P6
through corresponding charge check valve 635.
[0253] Referring to FIGS. 31(a), 31(b) and 32(a), a check valve 639
is disposed at a left end portion of fluid passage hole 699d. A
vertical fluid passage hole 636b is extended downward from an
intermediate portion of fluid passage hole 699d to a relief valve
636. Further, a fore-and-aft horizontal drain hole 636c is extended
from relief valve 636 and opened outward at the rear side surface
of charge pump casing 692. Check valve 636 absorbs excessive fluid
from fluid passage hole 699d through hole 636c and drains it to the
fluid sump through drain hole 636c. Referring to FIGS. 28 and
31(a), a vertical fluid passage hole 650a is extended downward from
fluid passage hole 699d to a relief valve 650. Further, a
fore-and-aft horizontal fluid passage hole 650b is extended from
relief valve 650 to delivery port 658b of charge pump 633. Relief
valve 650 absorbs excessive fluid from fluid passage hole 699d and
supplies it to delivery port 658b of charge pump. Further
description of check valve 639 and relief valves 636 and 650 is
omitted because they are similar to respective check valve 39 and
relief valves 36 and 50 in transaxle 1.
[0254] When transaxle 601 replaces rear transaxle 1 in each of the
foregoing vehicles 100 to 500, ports 601a , 601b, 675 and 676 are
disposed on the respective right outer ends of joint plugs 622a,
627a, 698a and 699a projecting rightwardly outward from the right
side wall of rear transaxle housing 601H. Therefore, pipes 23, 26,
81 and 82 can be compactly collected to be connected to respective
ports 601a , 60 1b, 675 and 676. Alternatively, for the arrangement
of vehicle 100 as shown in FIG. 5, transaxle 601 may be disposed so
that ports 601a , 601b, 675 and 676 are provided on the respective
left outer ends of joint plugs 622a, 627a, 698a and 699a projecting
leftwardly outward from the left side wall of rear transaxle
housing 601H.
[0255] As shown in FIG. 26, front axle-driving hydraulic fluid port
601a is disposed higher than rear axle-driving hydraulic fluid port
601b. As shown in FIGS. 27 and 32(b), port 601b is disposed
rightward from port 601a . Due to this arrangement of ports 601a
and 601b, pipes 23 and 27 connected to respective ports 601a and
601b are can be smoothly extended forwardly upward without
stressing bend, thereby being further compactly collected. Front
and rear auxiliary (power steering) device driving hydraulic fluid
ports 675 and 676 are disposed at the same height.
[0256] A mechanism for controlling the tilt angle and direction of
movable swash plate P6a of hydraulic pump P6, including speed
control arm 614, is omitted because it is similar to that of
transaxle 1. Additionally, as shown in FIG. 26, transaxle 601 is
provided with a shock absorber 614a, pivotally interposed between a
tip of speed control arm 614 and a right rear portion of transaxle
housing 601H. When depressed speed control pedal 13 is suddenly
released from the depression force, shock absorber 614a slows down
the neutral-returning motion of movable swash plate P6a, causing
abnormal stress onto engine 10 and the traveling power transmission
system, against the neutral-biasing force of a spring (coinciding
to spring 115).
[0257] In transaxle 601, control lever 614 and center section 691
may be provided with a mechanism for expanding a neutral dead zone
of hydraulic pump P6 relative to the tilt angle of swash plate P6a
similar to the mechanism including the orifice members having
orifices 171a , 172a fitted in center section 101 and groove 114a
formed in arm 114 as shown in FIG. 21.
[0258] Referring to FIG. 26, transaxle 601 is provided with a
forcible relief valve mechanism for draining fluid from the HST
circuit when the vehicle is towed or for another purpose, similar
to that shown in FIG. 19. In this regard, as shown in FIG. 26, a
forcible relief lever 761 is pivoted on housing 601H so as to
operate the forcible relief valve mechanism.
[0259] The flow of fluid in HST circuit HC1 (for driving axles 6
and 8 and for driving power steering cylinder 79) where transaxle
601 replaces rear transaxle 1, whether the vehicle travels forward
or backward, is omitted because it is similar to the foregoing flow
referring to FIG. 2, on the assumption that hydraulic pump P6 with
swash plate P6a and hydraulic motor M6 serve as hydraulic pump P
with swash plate Pa and hydraulic motor M1, respectively; fluid
passage hole 621 serves as passage 21; the fluid passage formed by
center section 691, adapter 693 and fluid passage plug 694 serves
as passage 22; joint pipe 627a and fluid passage holes 627b, 627d
and 627e constitute passage 27; fluid passage hole 698b and joint
plug 698a constitute passage 98; joint plug 699a and fluid passage
holes 699b and 699c constitute passage 99; and suction fluid
passage hole 631, fluid filter 632, charge pump 633, fluid passage
hole 634, check valves 635, relief valve 636, check valve 639 and
relief valve 650 serve as respective components 31, 32, 33, 34, 35,
36, 39 and 50.
[0260] The drive train from hydraulic motor M6 to axles 6 in
transaxle 601 is similar to that from hydraulic motor M1 to axles 6
in transaxle 1, on the assumption that motor shaft 727, gear 727b,
brake disc 740, deceleration gear train 637 and differential gear
unit 638 including a bull gear 638a and a differential side gear
638b serve as respective components 127, 127b, 140, 37, 38, 38a and
38b. Additionally, in transaxle 601, differential gear unit 638
comprises is provided with a differential lock mechanism, as shown
in FIG. 27. The differential lock mechanism comprises a
differential lock pin 638d and a shifter 638e. Shifter 638 is
manually operated from the outside of transaxle housing 601H, so as
to slide along (right) axle 6. Differential lock pin 638d
integrally movably engages with shifter 638d and is axially
slidably fitted in (right) differential side gear 638b. When
shifter 638e is operated for differential locking, shifter 638e
slides (leftward) so as to push differential lock pin 638d into a
hole of bull gear 638a through (right) differential side gear 638b,
as shown in FIG. 27, thereby locking (right) axle 6 to bull gear
638a, whereby left and right axles 6 become rotatable integrally
with each other. When shifter 638e is operated for canceling the
differential locking, shifter 638e slides rightward so as to
withdraw differential lock pin 638d from the hole of bull gear
638b, thereby allowing differential rotation of left and right
axles 6.
[0261] It is further understood by those skilled in the art that
the foregoing description is a preferred embodiment of the
disclosed apparatus and that various changes and modifications may
be made in the invention without departing from the spirit and
scope thereof defined by the following claims.
* * * * *